Add a GH Action for docs deployment to Pages

.github/workflows/pages.yml

+name: Deploy Sphinx documentation to Pages
+
+on:
+  push:
+    branches: [test]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v3
+    - uses: actions/setup-python@v3
+    - name: Install dependencies
+      run: pip install .[docs]
+    - name: Sphinx build
+      run: make -C doc html BUILDOUT=../_site
+    - name: Upload artifact
+      uses: actions/upload-pages-artifact@v3
+  deploy:
+    runs-on: ubuntu-latest
+    needs: build
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+    permissions:
+      pages: write
+      id-token: write
+    steps:
+    - name: Deploy to GitHub Pages
+      id: deployment
+      uses: actions/deploy-pages@v4