add more precise information for size
We already have this information in the dataset_infos.json files of each dataset.
Maybe we can parse these files in the backend to return their content with the endpoint at huggingface.co/api/datasets

For now if you want to access this info you have to load the json for each dataset. For example:
- for a dataset on github like `squad` 
-   https://raw.githubusercontent.com/huggingface/datasets/master/datasets/squad/dataset_infos.json
- for a community dataset on the hub like `lhoestq/squad`:
  https://huggingface.co/datasets/lhoestq/squad/resolve/main/dataset_infos.json
For the import into ELG, we would like a more precise description of the size of the dataset, instead of the current size categories. The size can be expressed in bytes, or any other preferred size unit. As suggested in the slack channel, perhaps this could be computed with a regex for existing datasets.