tools,doc: add support for several flavors of JS code snippets

Enable code example using both modern ESM syntax and legacy CJS syntax.
It adds a toggle on the web interface to let users switch from one
JavaScript flavor to the other.

PR-URL: https://github.com/nodejs/node/pull/37162


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>