docs(logger_level_reconfigure): update readme (#5471)

Signed-off-by: Takamasa Horibe <[email protected]>

common/tier4_logging_level_configure_rviz_plugin/README.md

@@ -3,3 +3,7 @@
 This package provides an rviz_plugin that can easily change the logger level of each node
 
 ![tier4_logging_level_configure_rviz_plugin](tier4_logging_level_configure_rviz_plugin.png)
+
+This plugin dispatches services to the "logger name" associated with "nodes" specified in YAML, adjusting the logger level.
+
+As of November 2023, in ROS 2 Humble, users are required to initiate a service server in the node to use this feature. (This might be integrated into ROS standards in the future.) For easy service server generation, you can use the [LoggerLevelConfigure](https://github.com/autowarefoundation/autoware.universe/blob/main/common/tier4_autoware_utils/include/tier4_autoware_utils/ros/logger_level_configure.hpp) utility.