The option tested are the following
It does not seem possible to render video directly onto the Github visualisation of the pages. But both are able to handle animated gif. The limitation of the animated gif is that there is no way to manipulate live the video (pause /rewind)
Markdeep is a tool based on markdown, which is directly rendered in most of the web browser. The positive point is that anyone can render it onto its machine with no particular installation. The drawback is that it is not rendered within the GitHub interface.