add onReady in typings

Author: yyx990803

types/router.d.ts

@@ -28,6 +28,7 @@ declare class VueRouter {
   back (): void;
   forward (): void;
   getMatchedComponents (to?: RawLocation): Component[];
+  onReady (cb: Function);
   addRoutes (routes: RouteConfig[]): void;
   resolve (to: RawLocation, current?: Route, append?: boolean): {
     location: Location;