Implement Chrome extension

[samdark]

The main action of the extension is to toggle "suggest to digest" state of the current opened browser tab.

1. It should automatically register a user account via API in case there's no token in local storage and store token that is received in response.
2. It should display grey icon if page is not within the database for current user.
3. It should display green icon if page is within database for current user.
4. Pressing grey icon takes current browser URL and submits it to API along with token.
5. Pressing green icon submits DELETE request for current browser URL along with token.