add Nh3Char(models.CharField)

[LouisKerdres]

hello

i need to have a CharField sanitized so I suggest this changes.

I'm not used to make PR on others repo, feel free to ask more modification to fit with your quality policy

rename Nh3Field in Nh3Text and deprecate the old naming too

[marksweb]

@LouisKerdres Apologies for the time it's taking for me to get to this!

I did start looking into the "textbook approach" to deprecating classes, having never actually needed to do that before.

I have also now remembered to assign this to myself so that will (hopefully) help me keep track of it.

[marksweb]

I've done a little research on the deprecation of a class now. So I think keep Nh3Field as a class.

Add a docstring note of the deprecation along with perhaps adding the typing decorator would be a good idea;

from typing import TypeVar
from typing_extensions import deprecated

@deprecated("Use Nh3Text instead")
class Nh3Field:
    """
    .. deprecated:: 0.2.0
       Use :class:`Nh3Text` instead.
    """
    pass

Then raise the deprecation in the __init__ similar to;

import warnings

class Nh3Field:
    def __init__(self):
        warnings.warn(
            "Nh3Field is deprecated and will be removed in a future version. Use Nh3Text instead.",
            DeprecationWarning,
            stacklevel=2
        )

And to prevent this being a breaking change, it could inherit Nh3Text;

class Nh3Field(Nh3Text):