Create GitHub Actions CodeQL workflow

[sherryhli]

Acceptance Criteria

• Create a GitHub Actions yml workflow file to run CodeQL
• Resolve high severity issues

Dev Notes

• CSRF middleware: http://expressjs.com/en/resources/middleware/csurf.html
• Rate limiting (nice-to-have)
  • https://www.npmjs.com/package/bottleneck
  • https://www.npmjs.com/package/limiter