Add redirect to landing page (facebook#4303)

Author: cipolleschi

website/static/_redirects

@@ -28,6 +28,7 @@
 /docs/the-new-architecture/backward-compatibility          https://github.com/reactwg/react-native-new-architecture#guides
 /docs/the-new-architecture/backward-compatibility-turbomodules https://github.com/reactwg/react-native-new-architecture#guides
 /docs/the-new-architecture/backward-compatibility-fabric-components https://github.com/reactwg/react-native-new-architecture#guides
+/docs/the-new-architecture/landing-page                    /architecture/landing-page
 /docs/new-architecture-intro                               https://github.com/reactwg/react-native-new-architecture#guides
 /docs/new-architecture-library-intro                       https://github.com/reactwg/react-native-new-architecture#guides
 /docs/new-architecture-library-android                     https://github.com/reactwg/react-native-new-architecture#guides