added implementation registration for stats

app/stats/config.proto

@@ -6,7 +6,12 @@ option go_package = "github.com/v2fly/v2ray-core/v4/app/stats";
 option java_package = "com.v2ray.core.app.stats";
 option java_multiple_files = true;
 
-message Config {}
+import "common/protoext/extensions.proto";
+
+message Config {
+  option (v2ray.core.common.protoext.message_opt).type = "service";
+  option (v2ray.core.common.protoext.message_opt).short_name = "stats";
+}
 
 message ChannelConfig {
   bool Blocking = 1;