Big rewrite for Manifest v3 (plus: dark mode)

[callumlocke]

• Supports Manifest v3 (essential to keep extension working beyond January 2023)
• Dark mode support
• Big refactor to modernise and pave the way for further development
  • Rewritten in TypeScript, code broken up a bit.
  • Removed complex dance between background/content script, because (a) can't make it work with Manifest v3 without completely changing the DOM-building approach, as service workers don't support DOM methods, (b) hopefully it's not needed so much now anyway as laptops have got a lot faster in the last 10 years, and (c) it makes the code a lot simpler.
• Pure CSS triangle icon to remove annoying 'request' for local PNG file in network tab
• Strings starting with / are now treated as links (previously only http:// and https:// strings got linked)
• Removed "Type JSON in console to inspect" feature (tricky to get it working with Manifest v3 approach... might be possible to re-enable this feature later using a service worker)
• Removed JSONP support, as it's pretty much obsolete these days and isn't worth the complexity.

Planning to publish this to the store soon... In the meantime, please try it out locally and leave a comment if it doesn't work

[apmeehan]

Strings starting with / are now treated as links (previously only http:// and https:// strings got linked)

Can't thank you enough for this update @callumlocke for this feature alone. Only noticed it by accident at work today, while working with our JSON API (which makes heavy use of endpoint links) and I can't tell you how much time this is going to save me from now on...

You don't happen to have any means of donating you a beer/coffee do you?