Integrate with restic

[merlinz01]

Is your feature request related to a problem? Please describe.
N/A

Describe the solution you'd like
I think it would be super nice if Timeshift would integrate with the restic backup tool.

Benefits/features of restic:

• It has a significant number of backup location types including S3 and SFTP.
• The restic program is a single-binary Go executable with an easy-to-use CLI interface.
• It encrypts everything based on a single password.
• On Linux it allows you to mount a snapshot on the file system for browsing or restoring.
• It's 100% open source (BSD 2-clause license).

For the UI, I would envision a third option for restic in the "Backup type" selection; and then in the "Location" page, a dropdown selector for the various location types that restic supports, with text entries for the location details depending on which type was selected.

Describe alternatives you've considered
Running restic manually or on a cron job, but that's not the point here.

Additional context
N/A