A userscript/greasemonkey script that adds a dynamic favicon to fastmail.com showing unread emails.
Tested in Firefox with Greasemonkey 2.3, doesn't work with Scriptish (due to CSP and not supporting @grant none).
Tested in Chrome with Tampermonkey 3.9.
If you have issues getting this working in another browser feel free to reach out.
I intentionally disabled autoupdating because you shouldn't trust that with something as important as your email. Check back for updates!
Please report all bugs.
https://openuserjs.org/scripts/middlerob/Fastmail_Favicon_Unread_Count