[Feature request] Ability to scrobble music to Last.fm

**Is your feature request related to a usage problem (not a bug)? Please describe.**
It would be great to have the ability to scrobble music listening to via FreeTube to Last.fm. There are browser plugins which can accomplish the same thing when listening to music on YouTube, so this theoretically should be possible.

**Describe the solution you'd like to see implemented**
A setting to authorise FreeTube to scrobble music listened to to your Last.fm account. Could either attempt to automatically recognise when a song / music video is being played, or provide a button for the user to instantly toggle a scrobble on for a particular video. Not sure the best UX around that.