doc: add methods to store

src/store/index.js

@@ -4,6 +4,13 @@ const state = reactive({
   user: null,
 });
 
+const methods = {
+  setUser(payload) {
+    state.user = payload ? payload.user : null;
+  },
+};
+
 export default {
   state,
+  methods,
 };