Add Django CSS/JS de-duplication

[Archmonger]

trafficstars

Description

Since CSS/JS is loaded as raw strings within a style tag, it's currently difficult to prevent duplicate loads.

This PR implements a simple server-side de-duplication algorithm for CSS and JS.

Checklist

Please update this checklist as you complete each item:

• [ ] Tests have been developed for bug fixes or new functionality.
• [ ] The changelog has been updated, if necessary.
• [ ] Documentation has been updated, if necessary.
• [ ] GitHub Issues closed by this PR have been linked.

_{By submitting this pull request I agree that all contributions comply with this project's open source license(s).}

[Archmonger]

Blocked on

• https://github.com/reactive-python/reactpy/issues/1198