Fix js installation step - malformed json

Closes #6107

website/docs/docs-Installing.mdx

@@ -43,9 +43,11 @@ import App from "./App";
 +     root: {
 +       stack: {
 +         children: [
-+           component: {
-+             name: 'com.myApp.WelcomeScreen'
-+           }
++           {
++             component: {
++               name: 'com.myApp.WelcomeScreen'
++             }
++           }  
 +         ]
 +       }
 +     }