* the front-end now use global constants, based on the translation key
* build-client.js use the ESBuild "define" directive to replace these
globals at compile time, by the english value
* build:client must now be called after build:languages
* moving the loadLoc and loc backend functions in a separate lib
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.
