[synapse] Add server to webproxy network

synapse/docker-compose.yaml

@@ -12,6 +12,7 @@ services:
       - LETSENCRYPT_HOST=matrix.jfreudenberger.de # the same domain as VIRTUAL_HOST; this enables ssl
     networks:
       - server
+      - webproxy
 
   postgresql:
     image: postgres:${postgres_version:-13}
@@ -32,3 +33,5 @@ volumes:
 networks:
   server:
     external: false
+  webproxy:
+    external: true