Use macbre/push-to-ghcr action

[macbre]

https://github.com/marketplace/actions/push-to-ghcr

+ docker image inspect ghcr.io/macbre/phantomas:latest
+ jq '.[].Config.Labels'
{
  "maintainer": "maciej.brencz@gmail.com",
  "org.label-schema.build-date": "2021-07-01T13:09:46Z",
  "org.label-schema.vcs-ref": "be678a0727a4c92a6b024bc440237c25787127c5",
  "org.label-schema.vcs-url": "https://github.com/macbre/phantomas.git",
  "org.opencontainers.image.revision": "be678a0727a4c92a6b024bc440237c25787127c5",
  "org.opencontainers.image.source": "https://github.com/macbre/phantomas"
}