Closes webpack dev server and exits process on "end" stdin (#7203)

Co-authored-by: Ian Schmitz <ianschmitz@gmail.com>

packages/react-scripts/scripts/start.js

@@ -164,6 +164,15 @@ checkBrowsers(paths.appPath, isInteractive)
         process.exit();
       });
     });
+
+    if (isInteractive || process.env.CI !== 'true') {
+      // Gracefully exit when stdin ends
+      process.stdin.on('end', function() {
+        devServer.close();
+        process.exit();
+      });
+      process.stdin.resume();
+    }
   })
   .catch(err => {
     if (err && err.message) {