expose vnode.child for backwards compat, update .flowconfig & ts types

Author: yyx990803

Diff for: .flowconfig

@@ -11,6 +11,7 @@
 flow
 
 [options]
+unsafe.enable_getters_and_setters=true
 module.name_mapper='^compiler/\(.*\)$' -> '<PROJECT_ROOT>/src/compiler/\1'
 module.name_mapper='^core/\(.*\)$' -> '<PROJECT_ROOT>/src/core/\1'
 module.name_mapper='^shared/\(.*\)$' -> '<PROJECT_ROOT>/src/shared/\1'

Diff for: src/core/vdom/vnode.js

@@ -48,6 +48,11 @@ export default class VNode {
     this.isCloned = false
     this.isOnce = false
   }
+
+  // DEPRECATED: alias for componentInstance for backwards compat.
+  get child (): Component | void {
+    return this.componentInstance
+  }
 }
 
 export const createEmptyVNode = () => {

Diff for: types/vnode.d.ts

@@ -17,7 +17,7 @@ export interface VNode {
   context?: Vue;
   key?: string | number;
   componentOptions?: VNodeComponentOptions;
-  child?: Vue;
+  componentInstance?: Vue;
   parent?: VNode;
   raw?: boolean;
   isStatic?: boolean;