This tells PIE to use the php_maxminddb-{version}-src.tgz tarball
from GitHub releases instead of the default ZIP download.
The pre-packaged source is required because PIE doesn't handle
git submodules when downloading from Composer/GitHub.
- Add composer.json with PIE configuration and build-path
- Add README.md with installation instructions
- Add main repo as submodule
- Add .gitignore for build artifacts
- Add LICENSE