add link to k8s docs on Missing Annotation page

plugins/kubernetes/src/Router.tsx

@@ -21,6 +21,7 @@ import { Route, Routes } from 'react-router-dom';
 import { rootCatalogKubernetesRouteRef } from './plugin';
 import { KubernetesContent } from './components/KubernetesContent';
 import { MissingAnnotationEmptyState } from '@backstage/core';
+import { Button } from '@material-ui/core';
 
 const KUBERNETES_ANNOTATION = 'backstage.io/kubernetes-id';
 const KUBERNETES_LABEL_SELECTOR_QUERY_ANNOTATION =
@@ -54,5 +55,20 @@ export const Router = (_props: Props) => {
     );
   }
 
-  return <MissingAnnotationEmptyState annotation={KUBERNETES_ANNOTATION} />;
+  return (
+    <>
+      <MissingAnnotationEmptyState annotation={KUBERNETES_ANNOTATION} />
+      <h1>
+        Or use a label selector query, which takes precedence over the previous
+        annotation.
+      </h1>
+      <Button
+        variant="contained"
+        color="primary"
+        href="https://backstage.io/docs/features/kubernetes/configuration#surfacing-your-kubernetes-components-as-part-of-an-entity"
+      >
+        Read Kubernetes Plugin Docs
+      </Button>
+    </>
+  );
 };