PR builds/checks for formats.kaitai.io
We currently do have a [CI pipeline set up](https://github.com/kaitai-io/kaitai_struct_formats/actions?query=workflow%3Aformats.kaitai.io) for https://formats.kaitai.io/ — and it even *runs* on PRs, but the result of that run is very hard to use.

For example, this is a [typical PR run](https://github.com/kaitai-io/kaitai_struct_formats/commit/e807ce1301f2e2b52a68665f5c4c725eeaa9c552/checks?check_suite_id=383058416) — it's the same as normal build (except for deployment phase). It runs "Build targets" phase, which runs ksc and ksc generates [log.json](https://github.com/kaitai-io/kaitai_struct_formats/suites/383058416/artifacts/933542) as artifact — that's it. There is currently no way to put that into distinct error messages and make it visibile inside the PR itself.

@KOLANICH, I believe, you've done some work in relation to utilizing GitHub actions to put some human-readable check messages/warnings into PR itself? Can you share/explain any details, is it something we can do here?