Support copying content in messages

Not sure if specific to OS, but after testing in Qubes-Whonix workstation I noticed copying messages was not working/supported

added T: feature label

Indeed this isn't specific to OS, but this functionality isn't yet implemented. I'll leave notes on how to implement it here.

• Gtk.Label.set_selectable() documentation

Briar GTK's interface is basically a fork of GNOME Fractal. They do it like this:

• message_menu.ui
• message_menu.rs
• connect_right_click_menu() in message widget

changed milestone to %GTK Next

changed milestone to %GTK 0.1.0-alpha2

mentioned in commit 0ed9ee3c

mentioned in merge request !43 (merged)

assigned to @nicoalt

closed via merge request !43 (merged)

mentioned in commit b310ce71

mentioned in commit 0b44129a

mentioned in merge request !46 (merged)

mentioned in commit 060d675d