add django-htmx

[biyeun]

Technical Summary

I will be using this dependency in an upcoming PR (for data cleaning)...

Specifically I will be making use of trigger_client_event and then HttpResponseClientRedirect in place of manually inserting headers as I'm doing at the moment.

Feature Flag

Safety Assurance

Safety story

just adding a dependency. code changes coming next

Automated test coverage

yes

QA Plan

n/a

Rollback instructions

• [x] This PR can be reverted after deploy with no further considerations

Labels & Review

• [x] Risk label is set correctly
• [x ] The set of people pinged as reviewers is appropriate for the level of risk of the change