Allow defining multiple hotkeys as one registration

[OliverJAsh]

A basic example is up/k and down/j. I want these to be defined as one hotkey registration so that in the shortcut palette I can render one grouped entry as opposed to multiple individual entries, e.g.

✅

↑/k up • ↓/j down

❌

↑ up • k up • ↓ down • j down