Add Support for Proton Drive about duplicati

[ts678]

"rclone got this working" has a lot disclaimers on it, according to Proton Drive page. It's reverse engineered.

No published stable API. no wish to release one, might do an SDK sometime. It should be in C# if we use it.
We’re three scientists who went from CERN to battling surveillance and Russian censorship at Proton. AMA..
The reply from their CTO sounds similar to the MEGA attitude, where they don't like third-party client code.
MEGA Security Update covers rclone bugs. Also read Mega Support: We don't share API anymore #5048.

IMO Duplicati backups are long-term and it's a big deal if something breaks. That's likely without a real API.
We've been bitten by other reverse-engineered third party efforts before. Jottacloud caused a lot of trouble.

If you want to take your chances with a backup, set up rclone, and set up the Duplicati Rclone storage type.