Add GitHub annotations

[tomzx]

Create a new output format that can be consumed by https://github.com/yuzutech/annotations-action (or a similar action).

See https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/collaborating-on-repositories-with-code-quality-features/about-status-checks#checks.

Since we already generate a JSON output for the changes detected, it should be only a matter of writing a new reporter, or taking the output of the JsonReporter of php-semver-checker and transforming it to match the expected format.