Extension help button

[argyleink]

need to have a keyboard master list readily available and leaning into context menus and ext icon buttons could be a great way to deliver that info.

[dotproto]

Adding an option to the context menu that appears when right clicking the extension's action button should be easy enough. I can take a shot at reading the source, building a list of keyboard shortcuts, and throwing together some rough HTML for a standalone tab or dialog window.

[argyleink]

Could send them to the Github wiki on click of the "help" or "hotkey list" button? Then we dont have to manage any UI? There's already context menu scaffolding, so given a contextmenu entry can punt to an absolute url, a v1 could be a tiny nice PR