fix(types): allow symbol & boolean for vnode key (vuejs#11914)

Author: Gavin-Gong

types/vnode.d.ts

@@ -20,7 +20,7 @@ export interface VNode {
   elm?: Node;
   ns?: string;
   context?: Vue;
-  key?: string | number;
+  key?: string | number | symbol | boolean;
   componentOptions?: VNodeComponentOptions;
   componentInstance?: Vue;
   parent?: VNode;