Figure out and document how to use devcontainer with GitHub codespace

I discovered that GitHub codespace also supports devcontainer.

https://github.com/nodejs/node/pull/60472#issuecomment-3467843933

This means for new Node.js contributors, they do not even need to download or install anything locally to start hacking on Node.js. Just click a few buttons on GitHub and they can start working on changes in the browser, and they can run tests in the container from the code space etc. as well. This might be very useful in code and learn sessions.

I don't know what extension codespace supports, but at least debugging the JS part of Node.js should be possible if the ports are set up correctly. One can always do command line debugging in the terminal in the code space as well. Or good old printing.

Codespace seems to be a paid feature but there's free tier available (?) so we'd be careful about directing people to it though

Beginne mit der Überprüfung der aktuellen devcontainer-Konfiguration und der verlinkten Node.js-Pull-Request-Diskussion über GitHub Codespaces. Dokumentiere die Schritte zum Öffnen des Projekts in einem Codespace, zum Ausführen von Tests und zum Debuggen. Weise dabei klar auf die verfügbaren Erweiterungen sowie auf etwaige Einschränkungen der kostenpflichtigen oder kostenlosen Stufe hin.