Add config flags to variants

variants/heltec_v3/platformio.ini

@@ -47,6 +47,9 @@ build_flags =
   -D ADVERT_LON=0.0
   -D ADMIN_PASSWORD='"password"'
   -D MAX_NEIGHBOURS=8
+;  -D BRIDGE_OVER_SERIAL=Serial2
+;  -D BRIDGE_OVER_SERIAL_RX=5
+;  -D BRIDGE_OVER_SERIAL_TX=6
 ;  -D MESH_PACKET_LOGGING=1
 ;  -D MESH_DEBUG=1
 build_src_filter = ${Heltec_lora32_v3.build_src_filter}