use child_process.stdio instead of the deprecated customFds to spawn man

Author: Feder1co5oave

bin/marked

@@ -20,7 +20,7 @@ function help() {
     cwd: process.cwd(),
     env: process.env,
     setsid: false,
-    customFds: [0, 1, 2]
+    stdio: 'inherit'
   };
 
   spawn('man', [__dirname + '/../man/marked.1'], options)