Repo metadata load and save (#339)
* repocard utilities + tests
* mix those methods on Repository
* handle case of no README.md inside repo
* suggestion from @osanseviero
Co-authored-by: Omar Sanseviero <osanseviero@users.noreply.github.com>
* tiny doc add
* `MODELCARD_NAME` => more general `REPOCARD_NAME`
* Additional test
Co-authored-by: Omar Sanseviero <osanseviero@users.noreply.github.com>
Co-authored-by: Lysandre <lysandre.debut@reseau.eseo.fr>
