[Docs] More explicit usage examples

[maelanleborgne]

We had a few issues opened by people who were confused on how to use the bundle.
The example in the doc was not using the standard "entrypoint / importmap" method from the AssetMapper component, and there was no mention of the ability to import TypeScript files from other JS/TS files.
The doc should definitely be more explicit on what the bundle can do and how to do it.
This is an attempt to clear things up, but I'm no documentation expert so any input would be appreciated :)