🔨 Add better pyvideo exports

[jefftriplett]

I noticed DjangoCon US has a few gaps on https://pyvideo.org/events.html

Since our unframework of a website's data is used in several non-DjangoCon conferences, there is some prior art to exporting the frontmatter data to a pyvideo-friendly format.

It might even be easier since we have pydantic support now, but here is a script that already does most of the heavy lifting: https://gitlab.com/pygotham/utils/-/blob/master/pyvideo/pyvideo-export.py