Fix some international keybindings (#2957)

This adds primitive interaction with the IME system for keyboard
shortcuts in zed.

- Consult the IME functionality when handling keyboard shortcuts. This
allows you to bind to characters (like " on a Brazillian keybaord, or $
on a Czech keyboard) that aren't typed with an unmodified key.
([#1981](https://github.com/zed-industries/community/issues/1981))
([#1913](https://github.com/zed-industries/community/issues/1913))

Co-authored-with: Antonio Scandurra <me@as-cii.com>