ci(docs): temporarily publish docs from feature branch

why: Preview sphinx_pytest_fixtures extension on live docs site.
what:
- Add sphinx-pytest-plugin-fixtures to docs.yml push branches
- TEMPORARY: revert before merging to master

Author: tony

.github/workflows/docs.yml

@@ -4,6 +4,7 @@ on:
   push:
     branches:
       - master
+      - sphinx-pytest-plugin-fixtures
 
 permissions:
   contents: read