FR: demonstrate Module Federation

https://webpack.js.org/concepts/module-federation/ aka. Micro-Frontends
is a way to break up a monolith app into several, which can then still be loaded at runtime into a Single Page Application.

This is typically used when several teams collaborate to build one app, and they either don't want to bundle their code together with other teams, or the scale is so large that memory and time required for the bundling step are unacceptable.

https://github.com/ScriptedAlchemy is an expert/evangelist of this approach, but not really involved in Bazel IIUC.

https://github.com/Aghassi/rules_spa is an example repo showing a POC of how to apply the concept.

Start with the webpack Module Federation documentation and the linked Aghassi/rules_spa proof of concept to understand the intended Bazel integration. Done should mean a demonstrated example showing independently built applications loaded at runtime into a single-page application, but the issue does not name files or tests.

Written by the indexing model from the issue text.