Add button alternative to shift+esc

[hoffr]

icons made by me in paint.NET, hope you like em. never touched javascript, web or extension code up until this point but i think it does what @simonlindholm on #11 suggested

[simonlindholm]

Ooh, lovely! Question is whether we want the button to be visible by default, but I guess it might be fine to make it so for discoverability's sake?

If you have a higher-res (48x48 or 96x96) version of that icon it would be nice to use the same icon for the extension itself: https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/manifest.json/icons I'm guessing you hand-drew it in 32x32 making that hard, though.

[hoffr]

I personally think many users would expect it to be visible by default, but it can easily be hidden via customize like with any other extension

Included in the latest commit is a paint.NET project file (.pdn) in case any edits are desired

[simonlindholm]

Yeah, I suppose, let's go with this. Thanks for the high-res icon and paint.NET project! I'll go ahead and merge this and publish a new release.