[Feature request]: Add hotkeys for shortcuts

We should setup hotkeys which execute specific shortcuts, similar to the hotkeys Superhuman offers.

Specifically:
- `e` to close the thread & move back to the thread list view
- arrows to move between threads
- `r` (or another, open to suggestions) to focus input on the human response input field
- `u` to undo changes in all inputs

Looking for a community contribution here!