Add webpack entry for the embedded API bundle

[mishraditi]

Description

This adds a webpack entry so the embedded API gets built into its own bundle.
It's the same setup as the existing external_api bundle, it just points at embedded_index.js and and builds it as a global called JitsiMeetEmbeddedAPI, so a host page can load embedded_api.min.js and use the API directly without an iframe.

The files it points at come from - jitsi-meet #17477

[jitsi-jenkins]

Hi, thanks for your contribution!
If you haven't already done so, could you please make sure you sign our CLA (https://jitsi.org/icla for individuals and https://jitsi.org/ccla for corporations)? We would unfortunately be unable to merge your patch unless we have that piece :(.