add loading

src/notice.js

@@ -0,0 +1,16 @@
+export default class Notice {
+  constructor(art) {
+    this.art = art;
+  }
+
+  show(msg) {
+    const { refs: { $notice } } = this.art;
+    $notice.style.display = 'block';
+    $notice.innerHTML = msg instanceof Error ? msg.message.trim() : msg;
+  }
+
+  hide() {
+    const { refs: { $notice } } = this.art;
+    $notice.style.display = 'none';
+  }
+}