Pinning pip requirements and added instructions for windows

[Tri125]

This PR contain 3 set of changes all aimed to make it easier to clone and start using the project.

1. I pinned specific versions in the requirements.txt file. Without specifying any version, pip was backtracking for over 10h trying to figure out which version of the dependencies to use. The versions could definitively be less strict but at the very least now it only takes a few second to setup. I would recommend testing on Linux/Docker before merging.
2. Since the README already mentioned the existence of the assets folder, I thought it would improve the experience for it to be part of the repository.
3. I documented the need to setup openh264 and FFmpeg for windows to be able to run the project.