Fix guidelines; switch version to 21

Version 20 (#32)

* Add translations
* New preferences window
* New about window
* Right-click menu

Allow installation on GNOME 43 (#30)

RunCat works on GNOME 43 as-is without any other changes.

Add support for GNOME 42 (#27)

* Update prefs.js (fixes #26)
* Update metadata.json to include support for GNOME 42
* Change version to 18

Fix TextDecoder initialization

Fix the runner stops running after lock/suspend (#22)

Add probable fix for issue #14

Add ability to scale the runner, add GNOME 41 support

Fix GNOME version in metadata

Bump version to 12