Enable htmx headers in CORS contexts

[jdevries3133]

Description

Hi! Thanks for all the work towards this great project.

In CORS contexts, headers need to be explicitly allowed for requests, and exposed for responses via the Access-Control-Allow-Headers and Access-Control-Expose-Headers headers, respectively. It might be handy if this library's middleware could take care of that through a simple boolean setting.

[adamchainz]

I maintain a separate library for CORS: https://github.com/adamchainz/django-cors-headers

I don't see anything htmx specific to do here. If there is something that you can't achieve with django-cors-headers, please elaborate.