Add docs and changes needed for local dev and test

[sinedied]

Note: hardcoded URL in frontend app was removed. It should not affect the prod environment with the <base href> added, but if it fails I can take a look why 😉 @cmaneu

[jdubois]

For tracking links we need to discuss, I'll add this in the Teams channel so everybody can see it

[sinedied]

Feel free to edit if needed. We can always add tracking after at once.

EDIT: I removed them

[jdubois]

Thanks @sinedied !