Initial rock implementation

[jardon]

• Please check if the PR fulfills these requirements

• [x] The commit message follows our guidelines

• [ ] Tests for the changes have been added (for bug fixes/features)

• [ ] Docs have been added / updated (for bug fixes / features)

• What kind of change does this PR introduce? (Bug fix, feature, docs update, ...) Feature

• What is the current behavior? (You can also link to an open issue here) No rock implementation is included in the repo.

• What is the new behavior (if this is a feature change)? Rockcraft should build and publish an OCI image to GHCR. All CI should run and the code should be linted using automated tooling.

• Does this PR introduce a breaking change? (What changes might users need to make in their application due to this PR?) Nope

• Other information: N/A

[dragomirp]

Now that the snap is published, I think we should merge this PR.