Add another signet electrum server

Running electrs v0.9.11 currently. TLS via nginx.
Always up-to-date info at http://ln.uk.ms/signet.txt

electrum/servers_signet.json

@@ -10,5 +10,11 @@
         "s": "50002",
         "t": "50001",
         "version": "1.4"
+    },
+    "bublina.eu.org": {
+        "pruning": "-",
+        "s": "60003",
+        "t": "50001",
+        "version": "1.4"
     }
 }