feat: make layout-independent shortcuts

[JarKz]

Related issues

Closes #121
Should resolve #146

Changes

• Added crate 'keycode' as dependency which helps us to use evdev keycodes.
• Implemented evdev keycode matching as fallback for shortcuts.

As maintainer said that the application should focus only to linux, so this changes on linux should work as remains, even on X11 (my friend has tested, but I'll accepts more tests). To match key uses Key from gtk4 as primary and fallbacks to use keycode which on linux is evdev keycode. That's why I've used the 'keycode' crate which have a list of evdev keycodes. This should make the shortcuts layout-independent.

Is it ready to merge?

I should make attention to fallback word. Maybe it is not correct way to use independent-layouts as default. I've asked in issue, but not got any answers and at this time I had draft code. So I implemented and can make changes if need to use config property.

[gabm]

I think we can go ahead with this like it is.. For current users i don't see a huge downside..

That being said, I can't estimate the consequences. If users start reporting bugs i am ready to revert this. Until then: let's go!