add action to release a version to ghcr after CI passes

[Nealium104]

• Should publish an image to https://github.com/uklibraries/exploreuk-web-app/pkgs/container/exploreuk-web-app.
• The image takes its tag from the commit where it was produced.
• It should only run when the CI task completes (not when it fails).
• Verified locally with act and a vagrant VM.

fixes #56

[nrsa222]

I added a ruleset to the dev branch which will only allow PRs for all merges (no force pushes) into the branch, and will require at 1 least approval from CODEOWNERS.

[nrsa222]

I set up a ruleset to require all pushes into the "dev" branch to be done through a PR and approval by CODEOWNERS. Once this is merged, double check that CI and package building works as expected with those new rules in place.