Yes, it's really happening, you're not dreaming..

An EARLY PREVIEW version for Firefox 55+ is ready for testing.

You can grab it here: kashev.me/da-notifier/

As noted on that page, this version may be broken, incomplete etc.
If I did everything correctly, it should auto-update when I have further FF fixes/adaptations.

If you're brave enough to test it, please report back on how it performs.

I will soon roll out the same version to Beta channel for Chrome.