Form field kwargs get ignored

[marksweb]

Describe the bug
If you definekwargs for a form field, models.BleachField.formfield doesn't always pass on those kwargs.

To Reproduce
Set a custom widget for a BleachField with no choices defined

Expected behavior
The kwargs should be updated, not overridden so that anything set outside of django-bleach isn't ignored & lost.

Screenshots
You can see here, a widget is passed in through kwargs but then kwargs aren't used in the returned field.