add widget name to render

[arturodelreal]

assign the new FroalaEditor to a constant in the javascript render.

[StevenMapes]

Can I suggest that this PR is changed so that the JS var is set by using the el_id and not a settings.py variable as if you have more than one instance on a page this will break as the code will try to define the constant multiple times. Though is it even needed as you can reload the instance by using let froala_editor_1 = FroalaEditor('#id_of_the_input_element');