chore: Add preview step to GitHub Pages deployment workflow

Author: Mearman

.github/workflows/build.yaml

@@ -64,6 +64,34 @@ jobs:
           path: public
           name: public
 
+  preview:
+    name: Preview when PR exists branch
+    runs-on: ubuntu-latest
+    needs: build
+    if: github.event_name == 'pull_request' && github.event.action != 'closed'
+    steps:
+      - name: Check out the repo
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Get artifacts from build job
+        uses: actions/download-artifact@v4
+        with:
+          name: public
+          path: public
+
+      - uses: actions/upload-pages-artifact@v3
+        with:
+          path: public
+          name: pages
+
+      - name: Deploy to GitHub Pages
+        uses: actions/deploy-pages@v4
+        with:
+          artifact_name: pages
+          preview: true
+
   deploy:
     if: github.ref == 'refs/heads/main'
     needs: build