a11y: Add accessibility to the keyboard layout

Sergio Costasrequested to merge
Sergio.Costas/tecla:a11y-add-accessibility-to-the-keyboard-layout-plucky into ubuntu/plucky

When pressing a key, a popup with all the possible combinations is shown, but the screen reader doesn't read it.

This patch generates a description of the popup and uses the gtk_accessible_announce() method to say it.

Fix: LP #2116166

Origin: https://gitlab.gnome.org/GNOME/tecla/-/merge_requests/32
Bug-Ubuntu: https://bugs.launchpad.net/ubuntu/+source/tecla/+bug/2116166

Merge request reports