Get rid of this.disposers while registering stuff in extensions (#1148)

Signed-off-by: Roman <ixrock@gmail.com>

extensions/support-page/main.ts

@@ -1,20 +1,14 @@
-import { LensMainExtension, Registry, windowManager } from "@k8slens/extensions";
+import { LensMainExtension, windowManager } from "@k8slens/extensions";
 import { supportPageURL } from "./src/support.route";
 
 export default class SupportPageMainExtension extends LensMainExtension {
-  async onActivate() {
-    console.log("support page extension activated")
-  }
-
-  async registerAppMenus(registry: Registry.MenuRegistry) {
-    this.disposers.push(
-      registry.add({
-        parentId: "help",
-        label: "Support",
-        click() {
-          windowManager.navigate(supportPageURL());
-        }
-      })
-    )
-  }
+  appMenus = [
+    {
+      parentId: "help",
+      label: "Support",
+      click() {
+        windowManager.navigate(supportPageURL());
+      }
+    }
+  ]
 }