Use setuptools_scm for versioning

Updates for compatibility with Django 4.0+

* Revise list of python versions for tox
* Use updated django url/path syntax
* Update for django 4.0+ compatibility
* Address indentation flagged by flake8
* Update tox.ini
* Allow a wider range of django versions
* Add basic github actions unit test with build matrix
* Remove import error checks for older versions of django
* Exclude incompatible python/django combinations from build matrix
* Add python 3.13 to test matrix
* Update python & Django classifiers to match tested versions
* Configure custom export action for custom export test case

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Co-authored-by: Chris Adams <cadams@loc.gov>
Co-authored-by: Ben Silverman <ben@performantsoftware.com>

Tag v1.0.2 !minor

chg: Remove Sphinx classes from the README to avoid PyPI errors !cosm…

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