update comments

Author: Shafiya-Heena

docker-compose.yml

@@ -1,3 +1,10 @@
+# https://github.com/docker/compose/issues/4513#issuecomment-281478365
+# >> Are we just expected to stay on [Docker Compose file format version 2] if
+# >> we want to use docker-compose and not swarm mode?
+# >
+# > Yes.
+#
+# https://docs.docker.com/compose/compose-file/compose-file-v2/
 version: '2.4'
 
 services: