Create automation to generate PRs updating restic version on restic releases

[garethgeorge]

Background

The UI is built against a specific version of restic. This ensures that changes to restic do not break the way the UI handles it's output (each UI release is validated with a single version of restic).

Proposal

Use https://github.com/marketplace/actions/create-pull-request and simple sed based automation to determine the latest version of restic and create a pull request if the hard coded version is out of date. Each time a PR is generated a new minor release should additionally be published that releases Restic UI with the latest minor version of restic.