Version 1.3.0

• Adds customisable colours: Set the addon to dark mode, light mode, or any colour scheme your heart desires
• Firefox only: Adds a sidebar containing a searchable list of all your bookmarks.
• Updates icons in the popup
• Backend stuff:
  • Updated to v1.2.0 of Mozilla's webextension-polyfill
  • Streamlined some more code
  • The icons were unicode characters before, now they are embedded SVG
  • Moved the filter functionality into appropriate class to try and reduce code duplication
  • Made background scripts not persistent (https://developer.chrome.com/extensions/event_pages)