Add GitLab CI, Node 20 Update and Cleanup
- Add GitLab CI
- Test on Node 20
- Remove `node-fetch`, `mocha-jscs`, and `mocha-jshint`
- Update Mocha to a more recent (but still outdated) version 4 (anything after this breaks tests?)
- Mocha tests hang in CI without --exit flag, unsure why
- Tests should be updated to begin with, they were (are?) extremely flaky when making this MR
- Update some deprecated `Buffer` calls
- Fix Docker testing
Edited by TChin