Regression test for inability to add resources in function-based transfomer

plugin/someteam.example.com/v1/starlarkmixer/mixer.star

@@ -0,0 +1,18 @@
+def run(r, fc):
+  for resource in r:
+    if resource.get("metadata") == None:
+      resource["metadata"] = {}
+    if resource["metadata"].get("annotations") == None:
+      resource["metadata"]["annotations"] = {}
+    resource["metadata"]["annotations"]["modified-by"] = fc["metadata"]["name"]
+
+  new = {
+    "kind": "ConfigMap",
+    "apiVersion": "v1",
+    "metadata": {
+      "name": "net-new"
+    }
+  }
+  r.append(new)
+
+run(ctx.resource_list["items"], ctx.resource_list["functionConfig"])