`L` is not JSON-serializable

The documentation for `L` claims that it is a drop-in for list operations.
Unfortunately, that's not entirely true, unlike true lists, `L` is not JSON-serializable:
```
Traceback (most recent call last):
File "/Users/criemen/repos/codeql-halo/plugins/custom_github/operators/actions.py", line 121, in workflow_finished
artifacts_str = xtras.dumps(artifacts)
File "/opt/homebrew/lib/python3.10/site-packages/fastcore/xtras.py", line 152, in dumps
return json.dumps(obj, **kw)
File "/opt/homebrew/Cellar/python@3.10/3.10.12/Frameworks/Python.framework/Versions/3.10/lib/python3.10/json/__init__.py", line 231, in dumps
return _default_encoder.encode(obj)
File "/opt/homebrew/Cellar/python@3.10/3.10.12/Frameworks/Python.framework/Versions/3.10/lib/python3.10/json/encoder.py", line 199, in encode
chunks = self.iterencode(o, _one_shot=True)
File "/opt/homebrew/Cellar/python@3.10/3.10.12/Frameworks/Python.framework/Versions/3.10/lib/python3.10/json/encoder.py", line 257, in iterencode
return _iterencode(o, 0)
File "/opt/homebrew/Cellar/python@3.10/3.10.12/Frameworks/Python.framework/Versions/3.10/lib/python3.10/json/encoder.py", line 179, in default
raise TypeError(f'Object of type {o.__class__.__name__} '
TypeError: Object of type L is not JSON serializable
```

This is rather annoying, as `ghapi` apparently returns `L` objects, instead of python lists, and besides a recursive traversal of the resulting object that I'd have to write myself, I've not found any easy way to convert an object/dist into something that I can JSON-serialize. Can you help me?
Is there any way you can make `L` work with JSON serialization? It doesn't work with `json.dumps`, and not even with your own `xtras.dumps` either 😞

Start by examining L and the xtras.dumps entry point, then reproduce the failure with Python's json.dumps and xtras.dumps as shown. Determine the supported conversion or serialization behavior for L objects, including nested values, and verify that the reported use case produces valid JSON.

Written by the indexing model from the issue text.