Specify the feature types of a dataset on the Hub without needing a dataset script
**Is your feature request related to a problem? Please describe.**
Currently if I upload a CSV with paths to audio files, the column type is string instead of Audio.

**Describe the solution you'd like**
I'd like to be able to specify the types of the column, so that when loading the dataset I directly get the features types I want.

The feature types could read from the `dataset_infos.json` for example.

**Describe alternatives you've considered**
Create a dataset script to specify the features, but that seems complicated for a simple thing.

cc @abidlabs 