[gtk4] implement a11y

Summary

The Orca screen reader reads something similar to

username@ComputerName: ~ GtkStackPagePanel GtkStackPagePanel KGX Terminal

when the terminal window is focused and doesn't read command output.

Typing, selecting text does not cause the screen reader to speak. I haven't found a way to get the screen reader to speak terminal output.

Note that gnome-terminal works with a screen reader.

Steps to reproduce

1. Enable the screen reader.
2. Open Console.
3. Type cd ~, press enter
4. Type echo "Hello, world", press enter
5. Scroll up with <ctrl>+<shift>+<up> and down with <ctrl>+<shift>+<down>
6. Open the search bar with <ctrl>+f
7. Type "world" and press enter.
8. Press enter.

Observed behavior

Screen reader only reads when the terminal is first focused and doesn't read terminal content.

Expected behavior

It should be possible to use the terminal without a visual display, as it is with gnome-terminal.

Specifically,

• The screen reader should echo keypresses. If I type a, the screen reader should say "a"
• The screen reader should read command output.
• When I move my cursor, in an application like ViM, the screen reader should read the content of the line I just moved the cursor to.
• When I search for text in the console, the screen reader should announce the number of matches and which match is currently focused.

System information

• Ubuntu 22.10, GNOME Console 43.0. Also tested on Manjaro with a recent version of Console.
• Screen reader: orca 43.0