Allow pathlib PoxisPath in Dataset.read_json
{'login': 'cccntu', 'id': 31893406, 'node_id': 'MDQ6VXNlcjMxODkzNDA2', 'avatar_url': 'https://avatars.githubusercontent.com/u/31893406?v=4', 'gravatar_id': '', 'url': 'https://api.github.com/users/cccntu', 'html_url': 'https://github.com/cccntu', 'followers_url': 'https://api.github.com/users/cccntu/followers', 'following_url': 'https://api.github.com/users/cccntu/following{/other_user}', 'gists_url': 'https://api.github.com/users/cccntu/gists{/gist_id}', 'starred_url': 'https://api.github.com/users/cccntu/starred{/owner}{/repo}', 'subscriptions_url': 'https://api.github.com/users/cccntu/subscriptions', 'organizations_url': 'https://api.github.com/users/cccntu/orgs', 'repos_url': 'https://api.github.com/users/cccntu/repos', 'events_url': 'https://api.github.com/users/cccntu/events{/privacy}', 'received_events_url': 'https://api.github.com/users/cccntu/received_events', 'type': 'User', 'site_admin': False}
[{'id': 1935892871, 'node_id': 'MDU6TGFiZWwxOTM1ODkyODcx', 'url': 'https://api.github.com/repos/huggingface/datasets/labels/enhancement', 'name': 'enhancement', 'color': 'a2eeef', 'default': True, 'description': 'New feature or request'}]
[]
[]
**Is your feature request related to a problem? Please describe.**
```
from pathlib import Path
from datasets import Dataset
ds = Dataset.read_json(Path('data.json'))
```
causes an error
```
AttributeError: 'PosixPath' object has no attribute 'decode'
```

**Describe the solution you'd like**

It should be able to accept PosixPath and read the json from inside.
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