CSV datasets should only read the CSV data files in the repo
When a no-script dataset has many CSV files and a JPG file, the library infers to use the Csv builder, but tries to read as CSV all files in the repo, also the JPG file.

I think the Csv builder should filter out non-CSV files when reading.

An analogue solution should be implemented for other packaged builders.

Related to:
- https://huggingface.co/datasets/abidlabs/img2text/discussions/1
- https://github.com/gradio-app/gradio/pull/3973#issuecomment-1545409061

CC: @abidlabs @severo 