One thing that seemed missing from the README was a mention of what persistence method is used for this. I'm guessing it's using the Chrome extension shared storage mechanism, but people who aren't familiar with extension development probably wouldn't be able to guess that.
Nice. Similar idea to this one a colleague built. <a href="https://chrome.google.com/webstore/detail/looks-good-to-me/hbiicpfmjknedfbhgpbckmmnbnmjknfo" rel="nofollow">https://chrome.google.com/webstore/detail/looks-good-to-me/h...</a>