Add docs workflow file (for testing).

.github/workflows/build_docs.yaml

@@ -0,0 +1,29 @@
+name: Build and deploy documentation
+on:
+  push:
+    branches:
+      - docs
+jobs:
+  build-docs:
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest]
+        python-version: ['3.10']
+    steps:
+      - uses: actions/checkout@v3
+      - name: Set up Python ${{ matrix.python-version }}
+        uses: actions/setup-python@v3
+        with:
+          python-version: ${{ matrix.python-version }}
+      - name: Install dependencies
+        run: |
+          python -m pip install -e .[development]
+      - name: Build docs
+        run: cd docs && make html
+      - name: Deploy to GitHub Pages
+        uses: peaceiris/actions-gh-pages@v3
+        with:
+          github_token: ${{ secrets.GITHUB_TOKEN }}
+          publish_dir: ./doc/build/html