Made Portainer network attachable

roles/portainer-deploy/templates/portainer-stack.yml.j2

@@ -1,5 +1,5 @@
 # vim: ft=yaml
-version: '3'
+version: '3.2'
 
 services:
   app:
@@ -42,6 +42,9 @@ services:
       - '/var/lib/docker/volumes:/var/lib/docker/volumes'
 
 networks:
+  default:
+    driver: overlay
+    attachable: true
   public:
     external: true