New in version 0.6.0:
- return from browser.storage.sync to browser.storage.local because of new size limits from mozilla

How to use:
- click on page action (inside an address bar) to add page to reading list
- click on browser action (button on a panel) to open sidebar
- for dark theme: click checkbox in preferences

- add sync to storage

- make sidebar toggleable
- add list icon for the browser action (now it's clear that it opens reading list)
- add popup after adding page
- removing now only possible through the list itself. Adding button just hoist page in the list