adding readme for datasets

[August-murr]

What does this PR do?

Fixes #2470

well, that was just not worth it.

Dataset cards can only be added manually so this PR adds a function that modifies it's Readme file and pushes it and I honestly doubt it was worth the complication.

Before submitting

• This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
• Did you read the contributor guideline,
  Pull Request section?
• Was this discussed/approved via a GitHub issue? Please add a link
  to it if that's the case.
• Did you make sure to update the documentation with your changes? Here are the
  documentation guidelines.
• Did you write any new necessary tests?

Who can review?

@qgallouedec