Update workflow to generate API docs

.github/workflows/gh-pages.yml

@@ -50,8 +50,9 @@ jobs:
         run: |
           pip install -q -r docs/requirements.txt
 
-      - name: Build docs
+      - name: Build API and docs
         run: |
+          sphinx-apidoc -fP -o docs/source/api optbeam
           sphinx-build -W --keep-going -b html -d docs/_build/doctrees docs/source docs/_build/html
           mv -v docs/_build/html public