more docs

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

docs/extensions/capabilities/common-capabilities.md

@@ -234,3 +234,25 @@ export default class ExampleExtension extends LensRendererExtension {
 }
 
 ```
+
+### Kubernetes Object Details
+
+An extension can register custom details (content) for specified Kubernetes kinds/apiVersions.
+
+``` typescript
+import React from "react"
+import { LensRendererExtension } from "@k8slens/extensions";
+import { CustomKindDetails, CustomKindDetailsProps } from "./src/custom-kind-details"
+
+export default class ExampleExtension extends LensRendererExtension {
+  kubeObjectMenuItems = [
+    {
+      kind: "CustomKind",
+      apiVersions: ["custom.acme.org/v1"],
+      components: {
+        Details: (props: CustomKindDetailsProps) => <CustomKindDetails {...props} />
+      }
+    }
+  ]
+}
+```