(ci) Break up building and deploying of docs

Author: josh-ashkinaze

.github/workflows/ci.yml

@@ -42,9 +42,35 @@ jobs:
         run: |
           pytest plurals/tests.py
 
-  build-and-deploy-docs:
+  build-docs:
     runs-on: ubuntu-latest
     needs: lint-and-test
+    if: github.event_name == 'pull_request' || github.event_name == 'push'
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v3
+
+      - name: Set up Python
+        uses: actions/setup-python@v4
+        with:
+          python-version: '3.9'
+
+      - name: Install dependencies
+        run: |
+          python -m pip install --upgrade pip
+          pip install -r dev_requirements.txt
+          pip install sphinx sphinx_rtd_theme
+
+      - name: Build Sphinx documentation
+        run: |
+          cd docs
+          make html
+
+  deploy-docs:
+    runs-on: ubuntu-latest
+    needs: build-docs
+    if: github.event_name == 'push' && github.ref == 'refs/heads/main'
 
     steps:
       - name: Checkout repository
@@ -70,4 +96,4 @@ jobs:
         uses: peaceiris/actions-gh-pages@v3
         with:
           github_token: ${{ secrets.GITHUB_TOKEN }}
-          publish_dir: docs/_build/html
+          publish_dir: docs/_build/html