Save certbot certificates in a separate volume

Signed-off-by: Marco Marinello <me@marcomarinello.it>

docker-compose.yml

@@ -26,6 +26,7 @@ services:
     volumes:
       - nextcloud:/var/www/html
       - nextclouddata:/var/www/nc_data
+      - nextcloudle:/etc/letsencrypt
     environment:
       POSTGRES_DB: nc
       POSTGRES_USER: ${POSTGRES_USER:-postgres}
@@ -50,3 +51,4 @@ volumes:
   postgres:
   nextcloud:
   nextclouddata:
+  nextcloudle: