chore: add maintainer

Signed-off-by: badai-nguyen <dai.nguyen@tier4.jp>

Author: badai-nguyen

perception/autoware_traffic_light_signals_merger/package.xml

@@ -7,6 +7,7 @@
   <maintainer email="yoshi.ri@tier4.jp">Yoshi Ri</maintainer>
   <maintainer email="masato.saeki@tier4.jp">Masato Saeki</maintainer>
   <maintainer email="dai.nguyen@tier4.jp">Dai Nguyen</maintainer>
+  <maintainer email="masato.saeki@tier4.jp">Masato Saeki</maintainer>
   <license>Apache License 2.0</license>
   <author email="dai.nguyen@tier4.jp">Dai Nguyen</author>