added missing property to child_process (#10997)

added missing property to child_process

node/node-4.d.ts

@@ -1036,6 +1036,7 @@ declare module "child_process" {
         pid: number;
         kill(signal?: string): void;
         send(message: any, sendHandle?: any): void;
+        connected: boolean;
         disconnect(): void;
         unref(): void;
     }