wip: root mount api compat

packages/shared/src/deprecations.ts

@@ -1,5 +1,7 @@
 export const enum DeprecationTypes {
-  DOM_TEMPLATE_MOUNT
+  DOM_TEMPLATE_MOUNT,
+  $MOUNT,
+  $DESTROY
 }
 
 type DeprecationData = {
@@ -14,6 +16,18 @@ const deprecations: Record<DeprecationTypes, DeprecationData> = {
       `In Vue 3, the container is no longer considered part of the template ` +
       `and will not be processed/replaced.`,
     link: `https://v3.vuejs.org/guide/migration/mount-changes.html`
+  },
+
+  [DeprecationTypes.$MOUNT]: {
+    message:
+      `vm.$mount() has been deprecated. ` +
+      `Use createApp(RootComponent).mount() instead.`,
+    link: `https://v3.vuejs.org/guide/migration/global-api.html#mounting-app-instance`
+  },
+
+  [DeprecationTypes.$DESTROY]: {
+    message: `vm.$destroy() has been deprecated. Use app.unmount() instead.`,
+    link: `https://v3.vuejs.org/api/application-api.html#unmount`
   }
 }