feat(kanata): Use C-ins/S-ins for copy/paste

[cypriani]

Rationale: those shortcuts are shell-friendly, unlike C-c/C-v.

[Nuclear-Squid]

I’ll have to look deeper into C-ins / S-ins, but S-del is way too dangerous in my eyes. I don’t think we even need a cut shortcut for the terminal (unless you’re in a text editor, who probably already has a shortcut for it)

[cypriani]

Updated commit to leave C-x for "cut".