Extensions: e2e test usePluginComponent hook (#91750)

* add simple test apps that use usePluginComponent hook and exposeComponent api

* add e2e test

* update readme

* Update README.md

* fix lint issue

* pr feedback

e2e/plugin-e2e/plugin-e2e-api-tests/as-admin-user/extensions/useExposedComponent.spec.ts

@@ -0,0 +1,9 @@
+import { test, expect } from '@grafana/plugin-e2e';
+
+const pluginId = 'myorg-componentconsumer-app';
+const exposedComponentTestId = 'exposed-component';
+
+test('should display component exposed by another app', async ({ page }) => {
+  await page.goto(`/a/${pluginId}`);
+  await expect(await page.getByTestId(exposedComponentTestId)).toHaveText('Hello World!');
+});