Generalize meta_path json file creation in load.py [#4540]
_The documentation is not available anymore as the PR was closed or merged._ @albertvillanova,  Can you please review this PR for Issue #4540  @lhoestq  Thank you for merging the PR . Is there a slack channel for contributing to the datasets library. I would love to work on the library and make meaningful contributions. Hi ! Sure feel free to join our discord ^^ 
https://discuss.huggingface.co/t/join-the-hugging-face-discord/11263 so that we can discuss together mor eeasily. Otherwise everything happens on github ;)
# What does this PR do?

## Summary

*In function `_copy_script_and_other_resources_in_importable_dir`, using string split when generating `meta_path` throws error in the edge case raised in #4540.*

## Additions
-

## Changes
- Changed meta_path to use `os.path.splitext` instead of using `str.split` to generalize code.

## Deletions
-
## Issues Addressed : 

Fixes #4540