To generate cert.key and cert.pem:

1. Remove web-platform.test.key and web-platform.test.pem in ../../certs.
2. From the root, run ./wpt serve --config tools/quic/certs/config.json and terminate it after it has started up.
3. Move tools/certs/web-platform.test.key to tools/quic/certs/cert.key.
4. Move tools/certs/web-platform.test.pem to tools/quic/certs/cert.pem.
5. Recover the original web-platform.test.key and web-platform.test.pem in ../../certs.

See also: ../../certs/README.md