Infer the features if missing
**Is your feature request related to a problem? Please describe.**

Some datasets, in particular community datasets, have no info file, thus no features.

**Describe the solution you'd like**

If a dataset has no features, the first loaded data (5-10 rows) could be used to infer the type.

Related: `datasets` would provide a way to load the data, and get the rows AND the features as the result.

**Describe alternatives you've considered**

The HF hub could also provide some UI to help the dataset maintainers to explicit the types of their rows, or automatically infer them as an initial proposal.