Merge pull request #3216 from ably/DX-286-kotlin-push-guide

[DX-286] Kotlin push guide

Author: GregHolmes

src/data/nav/pubsub.ts

@@ -264,6 +264,10 @@ export default {
               name: 'APNs',
               link: '/docs/push/getting-started/apns',
             },
+            {
+              name: 'FCM',
+              link: '/docs/push/getting-started/fcm',
+            },
           ],
         },
         {