Fix: attrs should be passed to __init__() of ResubmitBaseWidget's super class

[codeout]

Hi un1t, thanks for your great library.

I'd like to specify attrs in ResubmitFileWidget just like FileInput(attrs={'accept': 'image/*'}).

ImageField(widget=ResubmitFileWidget(attrs={'accept': 'image/*'}))

This PR allows us to reflect the given argument.

Note: Inheritance hierarchy

1. django.forms.Input
2. -> django.forms.FileInput
3. -> django.forms.ClearableFileInput
4. -> ResubmitBaseWidget

# https://github.com/django/django/blob/master/django/forms/widgets.py

class Input(Widget):
    def __init__(self, attrs=None):
        if attrs is not None:
            attrs = attrs.copy()
            self.input_type = attrs.pop('type', self.input_type)
        super().__init__(attrs)

[maddencs]

:+1: