feat: help key + broader keybinding modifier support

[Squirreljetpack]

Adds help key display and broader modifier support for keybindings.

Stacked on #167

[AMythicDev]

Do not base your commits on main branch. Either:

• Stack your PRs one after the another, for example stack this one above feat: configurable output sink #167 and feat: overrideable clipboard #169 on this so on and so forth. This will also show up on the GitHub UI. I would generally recommend this.
• Rebase each of your branches from the previous PR. This would initially show merge conflicts on the GitHub UI, but as I review and merge them, the conflicts would get resolved.

[Squirreljetpack]

Can't do 1 because I don't have write permissions here, so I chose 2. I think if you use merge instead of squash and merge the subsequent ones will resolve cleanly. btw, if they get there, the final pr has been updated to fix lints.

[AMythicDev]

Yeah it's fine, #167 is already good. You just needed to rebase the subsequent PRs which you already did as I see. I will review it now.