Add a minimal documentation?

[brayevalerien]

This project seems promising, especially due to the diring need of efficient dataset handling for generative AI model training. It seems to take an interesting approach and I would like to try it, but the lack of documentation makes it hard to addopt.

The source is currently mostly undocumented, so adding a proper documentation would help me and probably others in the future to use this solution.
Adding examples could be an alternative and would also help getting started with mgds.