add change note for mapper

Author: RollingOat

autonomy_core/map_plan/mapper/changelog.md

@@ -0,0 +1,15 @@
+# Changelog
+
+## [Unreleased]
+- Initial creation of `changelog.md` to track changes in the mapper module.
+
+## Files Changed
+- CMakelists.txt: use ament_cmake as build tools
+- package.xml
+- src/
+- include/
+
+## Note
+sensor_msgs::msg::pointcloud is still used in the code, suggested to migrate to pointcloud2 in the future
+
+Test relevant files are not updated in either the src file or compiled in CMAKELISTS.TXT