Some HTML files were importing iframe_api.js automatically by detecting the referrer document.
While this was done in a safe way (the map container does not use cookies), it is not
a best practice to load a script originating from document.referrer.
This PR solves the issue by using PHP to inject the correct domain name in the HTML files.
This would allow us to have tests that don't rely on the iframe_api.js from prod, and would allow scripts that target the correct iframe API, no matter if they are running on workadventu.re or on self-hosted maps.
Implementation of LayersFlattener
Implementation of Setting properties of a layer form script
Update show/hide layer form script
Update unit test of LayersIteratorTest
Adds a first version of an API to communicate between an iFrame opened by WorkAdventure and WorkAdventure itself.
The first API method is a method allowing to add messages in the chat, from the iFrame.
Comes with a test file.
