`ParamType` missing `name` errors on `to_info_dict`

[phy1729]

When calling to_info_dict on a ParamType instance which doesn't have a name attribute, an exception is raised. While this is a bug in the downstream code, only to_info_dict is affected, so the bug often goes unnoticed.

class TestType(click.ParamType):
    pass

TestType().to_info_dict()

>       return {"param_type": param_type, "name": self.name}
E       AttributeError: 'TestType' object has no attribute 'name'

src/click/types.py:66: AttributeError

It would be nice to have some sort of reasonable fallback. I've put coded such possibility at main...phy1729:fix-ParamType-no-name . I also fixed where the docs neglected to specify name in an example.

Environment:

• Python version: Python 3.9.9
• Click version: 8.0.3