This reviews and demonstrates how to embed MP4 videos with audio into README.md files hosted on github.com (this also works on private GitHub Enteprrise deployments).
The approach is to upload the video as an outside-of-git asset by dragging and dropping it into the file editor on github.com, which is the same way that embedded videos can be uploaded onto PRs / Issues / etc.
An advantage of this approach is that the video is then not part of the .git repo and does not make cloning the repository take longer.
Note that the audio is not enabled automatically so it is probably worth noting in the title for the videos that audio is included.
Note: be sure to unmute the audio
github-com-mp4-demo.mp4
Note: be sure to unmute the audio