Documentation

[quoid]

• update readme
• create video walkthrough for macOS
• create video walkthrough for iOS
• make help page bundled with iOS

[quoid]

Notes from #349 (from @turkishmaid):

Regarding what to be documented, my suggestion was not so much to explain about the user script itself (that's JavaScript, nuff said), but about what API the script actually has towards the hosting page, specific to exactly this tool I have installed, rather than sending me to google whether docs of other user script tools might reveal something that would also work here. A simple example for each API function would also great, sometimes even sufficient.