ci: add conditions and build artifact handling

Author: h2xd

.github/workflows/_tests.yml

@@ -24,6 +24,13 @@ jobs:
 
       - run: pnpm build
 
+      - name: 🔺 Upload frontend distribution artifacts
+        uses: actions/upload-artifact@v3
+        with:
+          name: build_distribution
+          path: theme/dist
+          if-no-files-found: error
+          retention-days: 1
 
   build_playground:
     needs: build
@@ -32,14 +39,21 @@ jobs:
     steps:
       - uses: actions/checkout@v3
 
+      - name: 🔻 Download build artifacts
+        uses: actions/download-artifact@v3
+        with:
+          name: build_distribution
+          path: theme/dist
+
       - uses: ./.github/actions/setup
 
       - run: pnpm build:testing
 
       - name: Upload artifact
+        if: github.ref == 'refs/heads/main'
         uses: actions/upload-pages-artifact@v1
         with:
-          path: './testing/dist/'
+          path: testing/dist
 
   unit_tests:
     name: 🧪 Unit Tests