Ensures key is properly passed to importedElements

The "key" prop was being lost in the trickle-down of importedElements.

Author: shawncrawley

src/js/packages/@reactpy/client/src/reactpy-vdom.tsx

@@ -133,6 +133,14 @@ export function createAttributes(
   model: ReactPyVdom,
   client: ReactPyClient,
 ): { [key: string]: any } {
+  // Add key to attributes
+  if (model.key) {
+    if (model.attributes) {
+      model.attributes['key'] = model.key
+    } else {
+      model.attributes = {'key': model.key}
+    }
+  }
   return Object.fromEntries(
     Object.entries({
       // Normal HTML attributes