[Feature Request] Improve keyboard accessibility

[sakkamade]

I think more keyboard shortcuts would significantly improve user experience.

Namely:

Shortcut	Action
Ctrl+q	Quit (as a supplement to Alt+F4)
F12 and fallback Ctrl+Shift+i	Dev Tools
Arrow Up/Down	Scroll through the list (without a need to click the item in list first)
Ctrl+Arrow Right/Left or/and Ctrl+Pg Up/Down	Change the filtering: All ⇄ Downloading ⇄ Pause ⇄ Finished
Ctrl+n (Ctrl+o)	Add new download (open "Add download" modal)
Ctrl+p	Settings
etc.