Keyboard shortcut for deleting a note

#598 was closed even though this wasn't implemented and people expressed an interest in this.

I personally would love to be able to hit `DELETE` key when my focus is on a note in the list and have it be trashed.

This is how the native macOS notes implements the feature.

Thanks 😄

No source files or tests are named. Start by tracing the focused note-list entry and the existing action that moves notes to trash, then review issue #598 and its discussion for prior context. Done means pressing DELETE while a note is focused moves that note to trash without affecting other contexts, with coverage for the shortcut.

Written by the indexing model from the issue text.