Fix panic when our device doesn't have election private keys

In cases where the user joins an election on another computer, we need to make
sure we don't panic merely because our device doesn't have the private keys to
fully verify sum+evals messages.  This change simply marks the verification
process of the election as failed.

In the future we can use something like SSSS to share keys between tallyard
devices.

Fix race condition in processing logic

This fixes the following nil pointer panic that happens when a message is being
processed but also requested in event.go.  I have no idea what I was thinking
with the `goto process` code in getAndHandleEvent ...

    waiting for evals...
    panic: runtime error: invalid memory address or nil pointer dereference
    [signal SIGSEGV: segmentation violation code=0x1 addr=0x190 pc=0x9eb25b]

    goroutine 1 [running]:
    tallyard.xyz/election.(*ElectionsMap).SetupEventHooks.func1.1(0x0, 0xc0010589c0)
	    /home/matrix/src/election/msg.go:153 +0x5b
    tallyard.xyz/election.(*EventStore).getAndHandleEvent(0xc000112340, 0xc000130030, 0x21, 0xc001a63b30, 0x2c, 0xc0b2f8, 0x12, 0x1, 0xc0014481e0, 0x0, ...)
	    /home/matrix/src/election/event.go:222 +0x176
    tallyard.xyz/election.(*EventStore).GetEvalsEvent(0xc000112340, 0xc000130030, 0x21, 0xc001a63b30, 0x2c, 0xc00025a030)
	    /home/matrix/src/election/event.go:163 +0x98
    tallyard.xyz/election.(*Election).SendSum(0xc001a80a00, 0xc000022620, 0xc000112340, 0x1, 0x1)
	    /home/matrix/src/election/voter.go:457 +0x4e4
    main.main()
	    /home/matrix/src/cmd/tallyard/main.go:181 +0xb46

Enable extra mautrix-go logging and bump mautrix-go for new logging

The bump is done to take advantage of the useful logging added in
https://github.com/mautrix/go/commit/3b28f2d

Log sync exits

Log sync errors

and decrease the sleep duration from 10 seconds [0] to 5 seconds.

[0]: https://github.com/mautrix/go/blob/v0.10.8/sync.go#L228

README: "libolm ... library" is redundant

README: mention need for libolm in source instructions

Bump version in README

Use gjson 1.10.2

See https://github.com/mautrix/go/issues/52

README: update mautrix-go URL

site: "dev mailing list" -> "mailing list"

site: put links on separate line from image and center those

Use fork of mautrix-go with bugfix

We're occasionally hitting the following error:

    panic: runtime error: slice bounds out of range [:208] with capacity 90 [recovered]
	    panic: runtime error: slice bounds out of range [:208] with capacity 90 [recovered]
	    panic: (*logrus.Entry) (0xbef2e0,0xc0000d2070)

    goroutine 1 [running]:
    github.com/sirupsen/logrus.(*Entry).log(0xc0001b62a0, 0x0, 0xc000464000, 0xf8f)
	    /home/matrix/go/pkg/mod/github.com/sirupsen/logrus@v1.8.1/entry.go:259 +0x2e2
    github.com/sirupsen/logrus.(*Entry).Log(0xc0001b62a0, 0x0, 0xc0004383f0, 0x1, 0x1)
	    /home/matrix/go/pkg/mod/github.com/sirupsen/logrus@v1.8.1/entry.go:293 +0x86
    github.com/sirupsen/logrus.(*Entry).Logf(0xc0001b62a0, 0xc000000000, 0xc0d38a, 0x1d, 0xc0004384a8, 0x2, 0x2)
	    /home/matrix/go/pkg/mod/github.com/sirupsen/logrus@v1.8.1/entry.go:338 +0xe2
    github.com/sirupsen/logrus.(*Logger).Logf(0xc0000d2e00, 0x0, 0xc0d38a, 0x1d, 0xc0004384a8, 0x2, 0x2)
	    /home/matrix/go/pkg/mod/github.com/sirupsen/logrus@v1.8.1/logger.go:151 +0x94
    github.com/sirupsen/logrus.(*Logger).Panicf(...)
	    /home/matrix/go/pkg/mod/github.com/sirupsen/logrus@v1.8.1/logger.go:192
    github.com/sirupsen/logrus.Panicf(...)
	    /home/matrix/go/pkg/mod/github.com/sirupsen/logrus@v1.8.1/exported.go:219
    tallyard.xyz/ui.RoomTUI.func1(0xc000308130)
	    /home/matrix/src/ui/tui.go:189 +0xe5
    panic(0xba8da0, 0xc00033e980)
	    /usr/lib/go/src/runtime/panic.go:679 +0x1b2
    github.com/rivo/tview.(*Application).Run.func1(0xc000358000)
	    /home/matrix/go/pkg/mod/github.com/rivo/tview@v0.0.0-20211202162923-2a6de950f73b/application.go:243 +0x82
    panic(0xba8da0, 0xc00033e980)
	    /usr/lib/go/src/runtime/panic.go:679 +0x1b2
    maunium.net/go/mautrix/crypto/canonicaljson.RawJSONFromResult(...)
	    /home/matrix/go/pkg/mod/maunium.net/go/mautrix@v0.10.8/crypto/canonicaljson/json.go:274
    maunium.net/go/mautrix/crypto/canonicaljson.sortJSONObject.func1(0x3, 0xc0003652c7, 0x9, 0xc0003652c8, 0x7, 0x0, 0xc7, 0x0, 0x0, 0x0, ...)
	    /home/matrix/go/pkg/mod/maunium.net/go/mautrix@v0.10.8/crypto/canonicaljson/json.go:113 +0x2b5
    github.com/tidwall/gjson.Result.ForEach(0x5, 0xc0003652c6, 0x55, 0x0, 0x0, 0x0, 0xc6, 0x0, 0x0, 0x0, ...)
	    /home/matrix/go/pkg/mod/github.com/tidwall/gjson@v1.12.1/gjson.go:293 +0x33d
    maunium.net/go/mautrix/crypto/canonicaljson.sortJSONObject(0x5, 0xc0003652c6, 0x55, 0x0, 0x0, 0x0, 0xc6, 0x0, 0x0, 0x0, ...)
	    /home/matrix/go/pkg/mod/maunium.net/go/mautrix@v0.10.8/crypto/canonicaljson/json.go:110 +0xe4
    maunium.net/go/mautrix/crypto/canonicaljson.sortJSONValue(0x5, 0xc0003652c6, 0x55, 0x0, 0x0, 0x0, 0xc6, 0x0, 0x0, 0x0, ...)
	    /home/matrix/go/pkg/mod/maunium.net/go/mautrix@v0.10.8/crypto/canonicaljson/json.go:62 +0x23b
    maunium.net/go/mautrix/crypto/canonicaljson.sortJSONObject(0x5, 0xc000365200, 0x11c, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, ...)
	    /home/matrix/go/pkg/mod/maunium.net/go/mautrix@v0.10.8/crypto/canonicaljson/json.go:136 +0x39d
    maunium.net/go/mautrix/crypto/canonicaljson.sortJSONValue(0x5, 0xc000365200, 0x11c, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, ...)
	    /home/matrix/go/pkg/mod/maunium.net/go/mautrix@v0.10.8/crypto/canonicaljson/json.go:62 +0x23b
    maunium.net/go/mautrix/crypto/canonicaljson.SortJSON(0xc000364fc0, 0x11c, 0x11c, 0xc0003650e0, 0x0, 0x11c, 0xc000364fc0, 0x11c, 0x11c)
	    /home/matrix/go/pkg/mod/maunium.net/go/mautrix@v0.10.8/crypto/canonicaljson/json.go:51 +0x1b1
    maunium.net/go/mautrix/crypto/canonicaljson.CanonicalJSONAssumeValid(0xc000364fc0, 0x11c, 0x11c, 0x120, 0xc000364ea0, 0x11c)
	    /home/matrix/go/pkg/mod/maunium.net/go/mautrix@v0.10.8/crypto/canonicaljson/json.go:42 +0xe0
    maunium.net/go/mautrix/crypto/canonicaljson.CanonicalJSON(0xc000364d80, 0x11c, 0x120, 0x11c, 0x120, 0x0, 0x0, 0x382a611eb390c)
	    /home/matrix/go/pkg/mod/maunium.net/go/mautrix@v0.10.8/crypto/canonicaljson/json.go:35 +0x8e
    tallyard.xyz/election.CalculateCommitment(0xc0004396e8, 0x1, 0x1, 0x20, 0x20, 0x20, 0x20)
	    /home/matrix/src/election/utils.go:42 +0x153
    tallyard.xyz/election.(*Election).JoinElection(0xc0000a6f00, 0xc0000e4460, 0xc000064140, 0x0, 0x0)
	    /home/matrix/src/election/voter.go:101 +0x24d
    tallyard.xyz/ui.RoomTUI.func4(0x0, 0xc05072, 0xf, 0xc10084, 0x21, 0xc000000000)
	    /home/matrix/src/ui/tui.go:268 +0x32f
    github.com/rivo/tview.(*List).InputHandler.func1(0xc00027a180, 0xc0003081b0)
	    /home/matrix/go/pkg/mod/github.com/rivo/tview@v0.0.0-20211202162923-2a6de950f73b/list.go:591 +0x278
    github.com/rivo/tview.(*Box).WrapInputHandler.func1(0xc00027a180, 0xc0003081b0)
	    /home/matrix/go/pkg/mod/github.com/rivo/tview@v0.0.0-20211202162923-2a6de950f73b/box.go:167 +0x5d
    github.com/rivo/tview.(*Application).Run(0xc000358000, 0x0, 0x0)
	    /home/matrix/go/pkg/mod/github.com/rivo/tview@v0.0.0-20211202162923-2a6de950f73b/application.go:335 +0x7db
    tallyard.xyz/ui.(*tallyardApplication).Run(...)
	    /home/matrix/src/ui/tui.go:594
    tallyard.xyz/ui.RoomTUI(0xc0002fe060, 0xc0000e4460, 0xc00025c010, 0xc0002fe000, 0xd02740, 0xc0000a0820, 0xc00025c010, 0x0, 0x0)
	    /home/matrix/src/ui/tui.go:285 +0x479
    main.main()
	    /home/matrix/src/cmd/tallyard/main.go:110 +0x7fb

My fork of mautrix-go at git.hnitbjorg.xyz has a patch that forgoes a gjson
optimization to prevent this issue.

See https://git.hnitbjorg.xyz/~edwargix/mautrix-go/commit/f4965a653a70 and
https://github.com/mautrix/go/issues/52 for further details.

Upgrade dependencies

go get -v -u -t ./...
go mod tidy

Upgrade gnark

Add hash commitments to messages to ensure integrity

This ensures that the content of events in an election are consistent between
senders and receivers.  This protects against malicious homeserver admins who
attempt to secretly edit events before they reach voters.

This also prevents exploitation of a bug in synapse where users can edit events
and thereby change their content while keeping the IDs the same; see
https://github.com/matrix-org/synapse/issues/10310 for details.

TUI: don't display user ID more than once if user rejoins

Don't panic in event handlers on nil event

This is causing panics in (*EventStore).getAndHandleEvent

Send human-readable event on election creation

TUI: properly handle panics inside goroutine