This uses pre-commit [1] to check patches are well formed and run
several linters on them. We currently do some boring things (check files
are syntactically valid) as well as some project-specific ones:
- Run illuaminate on the Lua files
- Run checkstyle on Java
[1]: https://pre-commit.com/
More importantly, `./gradlew check' actually runs the in-game tests,
which makes the CI steps look a little more sensible again.
Somewhat depressing that one of the longest files (15th) in CC:T is the
build script.
