Add keyboard shortcuts + popup shortcut guide

[ionleu]

What's the feature?

No keyboard shortcuts for extension actions. Everything has to be clicked manually.

How to reproduce

Try using a shortcut for any action—nothing happens.

What should happen?

Each action should have a keyboard shortcut. We should also show a shortcut guide popup, like the one ChatGPT has (Cmd + /).

Screenshots

N/A

Your setup

• OS: Any
• Browser: Chrome
• Node: 18.19.1

Anything else?

The shortcut popup should open with something like Cmd + / and list all available actions.

[KunalKumar-1]

@ionleu assign this issue to me