EBR-91: add package the ext section in build.yml

.github/workflows/build.yml

@@ -62,6 +62,14 @@ jobs:
         pip uninstall -y "tvb-ext-unicore" jupyterlab
         rm -rf myextension
 
+    - name: Package the extension
+      run: |
+        set -eux
+
+        pip install build
+        python -m build
+        pip uninstall -y "tvb-ext-unicore" jupyterlab
+
     - name: Run tests
       run: |
         pytest tvbextunicore -r ap