Call artifacts

We would ideally store the following artifacts per call:
* Agenda (currently GitHub Issue)
* Recording (currently Zoom/YouTube/ECH Institute X live stream & podcast)
* Raw transcript
* Raw chat log
* AI improved transcript
* Threaded chat log
* Moderator summary of decisions & action items
* Links to documents/presentations shared on the call

https://github.com/ethereum/pm was previously the home of call artifacts. We would ideally store all artifacts in one location, so that they are available forever.