Add gha workflow for docs (#20)

.github/workflows/docs.yml

@@ -0,0 +1,41 @@
+name: Docs
+
+on:
+  pull_request:
+    paths:
+      - 'docs/**'
+      - '.github/workflows/docs.yml'
+  push:
+    branches:
+      - main
+    paths:
+      - 'docs/**'
+      - '.github/workflows/docs.yml'
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+permissions:
+  contents: read
+
+jobs:
+  docs:
+    runs-on: ubuntu-22.04
+    name: docs
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v3
+
+      - name: Set up Python
+        uses: actions/setup-python@v4
+        with:
+          python-version: '3.11'
+          cache: 'pip'
+
+      - run: python -m pip install -e . [docs]
+
+      - name: Build docs
+        run: |
+          cd docs
+          sphinx-build -b spelling -n -q -W --keep-going -d _build/doctrees -D language=en_US -j auto . _build/spelling