Add support for passing extra HTML attributes from source element to template for field/display template Tag Helpers

[DamianEdwards]

E.g. make <editor class="form-control" for="FirstName" /> actually set the class inside the template.

[nfplee]

Hi Damian, I had a stab at doing something similar without any luck. See https://stackoverflow.com/questions/59504426/add-all-attributes-from-a-collection for more information.