add MessageChannel mock to grafana-plugin-configs

packages/grafana-plugin-configs/jest/jest-setup.js

@@ -84,3 +84,19 @@ global.ResizeObserver = class ResizeObserver {
     this.#isObserving = false;
   }
 };
+
+global.MessageChannel = jest.fn().mockImplementation(() => {
+  let onmessage;
+  return {
+    port1: {
+      set onmessage(cb) {
+        onmessage = cb;
+      },
+    },
+    port2: {
+      postMessage: (data) => {
+        onmessage?.({ data });
+      },
+    },
+  };
+});