chore: add github CI

[43081j]

Adds a simple build workflow to github CI.

This won't run the tests, only the build. until we add a root test script such that we can just pnpm test in /

Currently, we can't do pnpm run -r test since bun is missing. So we would need to decide if to install bun globally or use node, etc.

[hbjydev]

Couple notes I think should be looked into before merge, but otherwise LGTM :)

[mary-ext]

not too sure about the PR yet, partly not wanting to rely on GitHub for anything (this repository is really just a mirror that happens to accept issues and pull requests)

I'd probably make the CI tests only do LTS to be honest, and use mise to do the runtime installation, that way it would always reflect the actual dev environment.

[43081j]

you're likely to receive contributions over time, and that will be here on GitHub I imagine

so any kind of CI setup will be beneficial if you want those contributions

if you don't want contributions here, and would rather keep it wherever your "source" repo is, we can close this no problem

[hbjydev]

I'm in agreement with @43081j -- if you'd rather your main point isn't GitHub, imo move everything to Codeberg, but GitHub is likely where you'll get the vast majority of contrib & such from, so it makes sense to use it. Plus, Github Actions isn't exactly GitHub-specific, you could move the setup & such to a different CI tool later on easily.