Replacing webpack by ESBuild for client code compilation (as in the
official quickstart plugin).
So we can remove deprecated webpack dependencies.
Note: webpack is still used for ConverseJS build.
This may be removed soon.
Related to issue #122.
* init some shared functions (videoHasWebchat, parseConfigUUIDs)
* api/room: checking that video has live enabled
* fix promise handling in initChat function
* removing some 'use strict' that are no more necessary in typescript
