List filters in auto-generated documentation

[dbrgn]

Checklist

• I have verified that that issue exists against the master branch of Django REST framework.
• I have searched for similar issues in both open and closed tickets and cannot find a duplicate.
• This is not a usage question. (Those should be directed to the discussion group instead.)
• This cannot be dealt with as a third party library. (We prefer new functionality to be in the form of third party libraries where possible.)

Description

Feature request: The built-in auto-generated docs (rest_framework.documentation.include_docs_urls) should include a list of fields that can be filtered on. This list should match the filterable fields when clicking the "Filter" button in the DRF admin.