ImageFolder add option to ignore some folders like '.ipynb_checkpoints'
Maybe it would be nice to ignore private dirs like this one (ones starting with `.`) by default. 

CC @mariosasko  Maybe we can add a `ignore_hidden_files` flag to the builder configs of our packaged loaders (to be consistent across all of them), wdyt @lhoestq @albertvillanova?  I think they should always ignore them actually ! Not sure if adding a flag would be helpful @lhoestq But what if the user explicitly requests those files via regex?

`glob.glob` ignores hidden files (files starting with ".") by default unless they are explicitly requested, but fsspec's `glob` doesn't follow this behavior, which is probably a bug, so maybe we can raise an issue or open a PR in their repo? > @lhoestq But what if the user explicitly requests those files via regex?

Usually hidden files are meant to be ignored. If they are data files, they must be placed outside a hidden directory in the first place right ? I think it's more sensible to explain this than adding a flag.

> glob.glob ignores hidden files (files starting with ".") by default unless they are explicitly requested, but fsspec's glob doesn't follow this behavior, which is probably a bug, so maybe we can raise an issue or open a PR in their repo?

After globbing using `fsspec`, we already ignore files that start with a `.` in `_resolve_single_pattern_locally` and `_resolve_single_pattern_in_dataset_repository`, I guess we can just account for parent directories as well ?

We could open an issue on `fsspec` but I think they won't change this since it's an important breaking change for them.
**Is your feature request related to a problem? Please describe.**
I sometimes like to peek at the dataset images from jupyterlab. thus '.ipynb_checkpoints' folder appears where my dataset is and (just realized) leads to accidental duplicate image additions. I think this is an easy enough thing to miss especially if the dataset is very large.

**Describe the solution you'd like**
maybe have an option `ignore` or something .gitignore style
`dataset = load_dataset("imagefolder", data_dir="./data/original", ignore="regex?")`

**Describe alternatives you've considered**
Could filter out manually

