Merge pull request #5119 from rhysd/add-child_process-unref

Added unref() to child_process.ChildProcess in node.d.ts

node/node.d.ts

@@ -823,6 +823,7 @@ declare module "child_process" {
         kill(signal?: string): void;
         send(message: any, sendHandle?: any): void;
         disconnect(): void;
+        unref(): void;
     }
 
     export function spawn(command: string, args?: string[], options?: {