needs a slash, else url will look like this:
`j.src = 'https://domain.tldpackages/rocketchat_livechat/assets/rocket-livechat.js';`

Add the ability to set the default language for new users.
Admin can set server default language in admin/General section.

Most modern browser will issue a pre-flight request with HTTP OPTION method before the actual asynchronous POST.    This adds a CORS supporting option endpoint.