Allow extensions to define cluster features (#1125)

Signed-off-by: Jari Kolehmainen <jari.kolehmainen@gmail.com>

extensions/metrics-cluster-feature/renderer.tsx

@@ -0,0 +1,25 @@
+import { Registry, LensRendererExtension } from "@k8slens/extensions"
+import { MetricsFeature } from "./src/metrics-feature"
+import React from "react"
+
+export default class ClusterMetricsFeatureExtension extends LensRendererExtension {
+  registerClusterFeatures(registry: Registry.ClusterFeatureRegistry) {
+    this.disposers.push(
+      registry.add({
+        title: "Metrics Stack",
+        components: {
+          Description: () => {
+            return (
+              <span>
+                Enable timeseries data visualization (Prometheus stack) for your cluster.
+                Install this only if you don't have existing Prometheus stack installed.
+                You can see preview of manifests <a href="https://github.com/lensapp/lens/tree/master/extensions/lens-metrics/resources" target="_blank">here</a>.
+              </span>
+            )
+          }
+        },
+        feature: new MetricsFeature()
+      })
+    )
+  }
+}