Still not working, but we surely need this...

Fixes #67.

On suggestions by yahoe.001 and anm on Transifex.

Credits of those texts go to:
* https://code.briarproject.org/briar/briar/-/blob/4e5f2e31df85cb6d56559bb99bc921d322f6a1af/TRANSLATION.md
* !65 (comment 41992)

Related to #65

Related to #66

Followup to !63

Closes https://code.briarproject.org/briar/briar-gtk/-/milestones/4

This reverts commit 9bfa6155.

Closes #54

Fixes #63.

The username and time in messages will be shown if either
* the author changes
* or the time difference of two messages is greater than 60 seconds

Closes #53.

Related to #53. This already improves UX a lot, but I still think we
should omit the username if it doesn't change between messages. Thinking
about it, we could even omit the time if it doesn't change.

The color used is Briar's primary "Lime" color, as per
* https://briar-styleguide.netlify.app/brand/
* https://code.briarproject.org/briar/briar-styleguide/-/blob/2e8fa50a2628ce685ad2a3c88337388b29f496ba/layouts/partials/brand/colors.html#L15

Fixes #62.

Fixes #60. Now we need to either implement #63 or #64.

Fixes #12

In preparation to future notification logic, the urgency hint should
already get their own logic.

Related to ff4e91e4 and #57.

Using GTK's Window.set_urgency_hint: https://lazka.github.io/pgi-docs/#Gtk-3.0/classes/Window.html#Gtk.Window.set_urgency_hint

Additional info: https://specifications.freedesktop.org/wm-spec/wm-spec-latest.html#URGENCY

Closes #57.

Related to #27.

Related to #27.

As of August 7, [a first beta release is available](https://mamot.fr/@KekunPlazas/104648142113069390).

The code to build can now be downloaded from [gnome.org](https://download.gnome.org/sources/libhandy/0.90/).

A [migration guide](https://gnome.pages.gitlab.gnome.org/libhandy/hdy-migrating-0-0-to-1.html) is available, just as [packages for Debian](https://packages.debian.org/bullseye/libhandy-1-0).

Fixes #59.

It's much easier to maintain like that.

Also add Arabic.