Adds .gitea/workflows/check.yml that runs docker build on push,
matching the standard CI pattern used across all sneak/* repos.
The Dockerfile already runs make check (fmt-check, lint, test)
so a successful build implies all checks pass.
Removes `vendor.tzst` and `modcache.tzst` that should never have been committed. Adds both to `.gitignore`.
Reviewed-on: #35
Co-authored-by: clawbot <sneak+clawbot@sneak.cloud>
Co-committed-by: clawbot <sneak+clawbot@sneak.cloud>
clawbot