`def has_array_namespace(obj) -> TypeIs[HasNamespace]`

[jorenham]

I'm not sure if has_namespace is the best name for this typeguard, so Suggestions are welcome.

Example implementation that builds #17:

# _namespace.py
from typing_extensions import TypeIs

# --snip--

def has_namespace(obj: object, /) -> TypeIs[HasNamespace[Any]]:
    return hasattr(obj, "__array_namespace__")

[nstarman]

Given https://data-apis.org/array-api-compat/helper-functions.html#array_api_compat.array_namespace and that there's the linalg namespace, how about the more verbose has_array_namespace.