Verify plugin examples from slot `README`s are valid

[brian-smith-tcril]

I tried using the example code from https://github.com/openedx/frontend-app-learner-dashboard/tree/frontend-base/src/slots/CourseBannerSlot by updating site.config.dev.tsx to be

-import { EnvironmentTypes, SiteConfig, footerApp, headerApp, shellApp } from '@openedx/frontend-base';
+import { EnvironmentTypes, WidgetOperationTypes, SiteConfig, footerApp, headerApp, shellApp } from '@openedx/frontend-base';
 
 import { learnerDashboardApp } from './src';
 
+import { Alert } from '@openedx/paragon';
+
 import '@openedx/frontend-base/shell/style';
 
+const myComponent = ({ cardId }) => (
+  <Alert variant="info" className="mb-0">
+    Course banner for course with {cardId}
+  </Alert>
+)
+
 const siteConfig: SiteConfig = {
   siteId: 'learner-dashboard-dev',
   siteName: 'Learner Dashboard Dev',
@@ -17,7 +25,17 @@ const siteConfig: SiteConfig = {
     shellApp,
     headerApp,
     footerApp,
-    learnerDashboardApp
+    {
+      ...learnerDashboardApp,
+      slots: [
+        {
+          slotId: 'org.openedx.frontend.slot.learnerDashboard.courseCardBanner.v1',
+          id: 'my.widget',
+          op: WidgetOperationTypes.REPLACE,
+          component: myComponent
+        },
+      ]
+    },
   ],
   externalRoutes: [
     {

and got

adding relatedId: 'defaultContent', fixes the error. I'm not sure if that is supposed to be required for using WidgetOperationTypes.REPLACE or not