Expose webserver_port to the native API (#2640)

esphome/components/api/api_connection.cpp

@@ -759,6 +759,9 @@ DeviceInfoResponse APIConnection::device_info(const DeviceInfoRequest &msg) {
 #ifdef ESPHOME_PROJECT_NAME
   resp.project_name = ESPHOME_PROJECT_NAME;
   resp.project_version = ESPHOME_PROJECT_VERSION;
+#endif
+#ifdef USE_WEBSERVER
+  resp.webserver_port = WEBSERVER_PORT;
 #endif
   return resp;
 }