Feature request: Passing specifc config to CaptchaField

[Pyvonix]

Hi,

Thank for the great library. I use it since a while.

I look for a way to pass specific config to one CaptchaField, and not as default config!

We could imagine a use case, where users want to use different generators or apply different length on some forms.
But in the current design this only possible to modify all captcha, not only one.

Example wished forms.py:

class SomeForm:
    captcha = CaptchaField(label='Captcha',
                                           required=True,
                                           config={"CAPTCHA_LENGTH": 8,
                                                        "CAPTCHA_CHALLENGE_FUNCT": "captcha.helpers.random_char_challenge"})

Did you envisage that kind of improvement?

Thank