Runnable Docker/Podman Container

From this release on, a container will created with each release that allows using imap-backup with a sole dependency: Docker or Podman.

Example:

docker run -v ./my-data:/data -ti ghcr.io/joeyates/imap-backup:latest \         
  imap-backup single backup \                                                   
  --email me@example.com --password mysecret --server imap.example.com \        
  --path /data/me_example.com