Need easier way to pass along kwargs with same name as a named arg

[wch]

Python doesn't like it if a kwarg has the same name as an explicitly named argument. This can cause problems when a function passes kwargs to a tag function, when the call to the tag function has a named argument like class_. For example:

from htmltools import *

def foo(text, **kwargs):
    return div(text, class_="foo", **kwargs)

foo("hi")
#> <div class="foo">hi</div>

foo("hi", class_="extra_class")
#> TypeError: htmltools.tags.div() got multiple values for keyword argument 'class_'

One possibility is for the tag function to accept a dict and merge it in with its kwargs.