Change base Typescript example to include AppStore type (#4704)

Author: EskiMojo14

docs/usage/UsageWithTypescript.md

@@ -65,10 +65,12 @@ export const store = configureStore({
 })
 
 // highlight-start
+// Get the type of our store variable
+export type AppStore = typeof store
 // Infer the `RootState` and `AppDispatch` types from the store itself
-export type RootState = ReturnType<typeof store.getState>
+export type RootState = ReturnType<AppStore['getState']>
 // Inferred type: {posts: PostsState, comments: CommentsState, users: UsersState}
-export type AppDispatch = typeof store.dispatch
+export type AppDispatch = AppStore['dispatch']
 // highlight-end
 ```