Closes #6328: Local docs build (#6769)

* Incorporate local documentation build in upgrade script

* Add docs build to CI

* Include docs build path in revision control

* Update footer dcos link

* Changelog for #6328

* Clean up errant links

.github/workflows/ci.yml

@@ -40,6 +40,9 @@ jobs:
         pip install pycodestyle coverage
         ln -s configuration.testing.py netbox/netbox/configuration.py
 
+    - name: Build documentation
+      run: mkdocs build
+
     - name: Collect static files
       run: python netbox/manage.py collectstatic --no-input