Where can I find the external API source code?

I attempted downloading the sourcec code from the source map, but it is in JSDoc/Flow and I have no idea how to build that.

All the source-code is here: GitHub - jitsi/jitsi-meet: Jitsi Meet - Secure, Simple and Scalable Video Conferences that you use as a standalone app or embed in your web application.
And latest external API you can find here jitsi-meet/modules/API/external at master · jitsi/jitsi-meet · GitHub