Grafana UI: Add warning info to the unstable package (#68388)

packages/grafana-ui/src/unstable.ts

@@ -1 +1,12 @@
+/**
+ * THESE COMPONENTS MUST NOT BE USED EXTERNALLY OR IN PLUGINS.
+ *
+ * Unstable components are still in development and are subject to breaking changes
+ * at any point, like feature flags but for components. They must only be used in
+ * Grafana core where we can coordinate changes.
+ *
+ * Once mature, they will be moved to the main export, be available to plugins, and
+ * be subject to the standard policies
+ */
+
 export * from './components/Text/TextElements';