Follow guidance for typing

src/shims-vue.d.ts

@@ -1,4 +1,12 @@
+import type { HelloStore } from "./store";
+
 declare module "*.vue" {
   import Vue from "vue";
   export default Vue;
 }
+
+declare module "@vue/runtime-core" {
+  interface ComponentCustomProperties {
+    $store: HelloStore;
+  }
+}

src/store/index.ts

@@ -11,9 +11,13 @@ const state: RootState = {
   message: "olleH",
 };
 
-export default new Vuex.Store({
+const store = new Vuex.Store({
   state,
   mutations: {},
   actions: {},
   modules: {},
 });
+
+export type HelloStore = typeof store;
+
+export default store;