Extend a django base template directly.

[pelme]

When wanting to use htpy with a django project with existing templates, it would be nice to have a helper to directly extend a django base template, something like:

import htpy as h
from htpy.django import extend_template

result = template_extend(
    'admin/base_site.html',
    breadcrumbs=h.div(".breadcrumbs"),
    coltype="colM",
    content=div('.module.report')[...],
) # result is a string with the blocks filled in. 

This can probably be implemented by just creating a template string dynamically like f"{{% extends {base_template}" %}}" and then creating a bunch of f"{{% block {name} %}}{htpy_contents}{{% endblock %}}"s dynamically and then passing that string to Template(X).render(..)`

[pelme]

the values needs to be passed via context and not passed directly to Template to avoid security problems. how to deal with {{ block.super }} though? maybe it cannot be supported