Add `rest-server`

[Veerendra]

• https://github.com/restic/rest-server
• https://github.com/restic/rest-server/blob/master/examples/compose-with-grafana/docker-compose.yml

[Veerendra]

Examples

$ restic -r rest:https://host:8000/ init
$ restic -r rest:https://user:pass@host:8000/ init
$ restic -r rest:https://user:pass@host:8000/my_backup_repo/ init