json encoding of option should use DjangoJSONEncoder

[tisdall]

django-froala-editor/froala_editor/widgets.py

Line 56 in e70b402

json_options = json.dumps(options)

The json encoding should use django.core.serializers.json.DjangoJSONEncoder so lazy components from settings can properly be evaluated.

For example, I'm trying to set imageManagerLoadURL using reverse_lazy. However, the default encoding gives a traceback when it encounters the reverse_lazy. If it used DjangoJSONEncoder then it would work properly.

from django.core.serializers.json import DjangoJSONEncoder
json_options = json.dumps(options, cls=DjangoJSONEncoder)