title: Add API code examples for loading methods
comments: The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/datasets/pr_4300). All of your documentation changes will be reflected on that endpoint.
body: This PR adds API code examples for loading methods, let me know if I've missed any important parameters we should showcase :)
  
  I was a bit confused about `inspect_dataset` and `inspect_metric`. The `path` parameter says it will accept a dataset identifier from the Hub. But when I try the identifier `rotten_tomatoes`, it gives me:
  
  ```py
  from datasets import inspect_dataset
  inspect_dataset('rotten_tomatoes', local_path='/content/rotten_tomatoes')
  
  FileNotFoundError: Couldn't find a dataset script at /content/rotten_tomatoes/rotten_tomatoes.py or any data file in the same directory.
  ```
  
  Does the user need to have an existing copy of `rotten_tomatoes.py` on their local drive (in which case, it seems like the same option as the first option in `path`)?