[FIX] move error handling out of fiber, fix complicated mounted issues

src/app/app.ts

@@ -1,3 +1,4 @@
+import { onError, onMounted } from "../component/lifecycle_hooks";
 import { Component } from "../component/component";
 import { ComponentNode } from "../component/component_node";
 import { MountOptions } from "../component/fibers";
@@ -64,8 +65,16 @@ export class App<T extends typeof Component = any> extends TemplateSet {
       throw new Error("Cannot mount a component on a detached dom node");
     }
     const node = new ComponentNode(this.Root, this.props, this);
+    const promise: any = new Promise((resolve, reject) => {
+      onMounted(() => resolve(node.component));
+      onError((e) => {
+        reject(e);
+        throw e;
+      });
+    });
     this.root = node;
-    return node.mountComponent(target, options);
+    node.mountComponent(target, options);
+    return promise;
   }
 
   destroy() {