Setup code sandboxed for examples / guides

Objective:
Add a sandbox to each guide where someone can play with the final result in the sandbox.

Potential services to use:
- https://codepen.io/
- https://jsfiddle.net/
- https://replit.com/

Reference: https://github.com/waku-org/js-waku-examples/issues/163#issuecomment-1783616883