Bump the npm_and_yarn group in /site with 3 updates

Bumps the npm_and_yarn group in /site with 3 updates: [express](https://github.com/expressjs/express), [send](https://github.com/pillarjs/send) and [serve-static](https://github.com/expressjs/serve-static).


Updates `express` from 4.19.2 to 4.21.0
- [Release notes](https://github.com/expressjs/express/releases)
- [Changelog](https://github.com/expressjs/express/blob/4.21.0/History.md)
- [Commits](expressjs/express@4.19.2...4.21.0)

Updates `send` from 0.18.0 to 0.19.0
- [Release notes](https://github.com/pillarjs/send/releases)
- [Changelog](https://github.com/pillarjs/send/blob/master/HISTORY.md)
- [Commits](pillarjs/send@0.18.0...0.19.0)

Updates `serve-static` from 1.15.0 to 1.16.2
- [Release notes](https://github.com/expressjs/serve-static/releases)
- [Changelog](https://github.com/expressjs/serve-static/blob/v1.16.2/HISTORY.md)
- [Commits](expressjs/serve-static@v1.15.0...v1.16.2)

---
updated-dependencies:
- dependency-name: express
  dependency-type: indirect
  dependency-group: npm_and_yarn
- dependency-name: send
  dependency-type: indirect
  dependency-group: npm_and_yarn
- dependency-name: serve-static
  dependency-type: indirect
  dependency-group: npm_and_yarn
...

Signed-off-by: dependabot[bot] <[email protected]>