* Add checked convert_to_nanoseconds() function (#145 <https://github.com/ros2/rcpputils/issues/145>)
* Add missing sections in docs/FEATURES.md TOC (#151 <https://github.com/ros2/rcpputils/issues/151>)
* [env] Add set_env_var function (#150 <https://github.com/ros2/rcpputils/issues/150>)
* Add missing cstddef include (#147 <https://github.com/ros2/rcpputils/issues/147>)
* Add accumulator test to CMakeLists.txt (#144 <https://github.com/ros2/rcpputils/issues/144>)
* rcpputils::fs: Fix doxygen parameter identifier (#142 <https://github.com/ros2/rcpputils/issues/142>)
* Make thread safety macro C++ standards compliant (#141 <https://github.com/ros2/rcpputils/issues/141>)
* Fix API documentation for clean rosdoc2 build (#139 <https://github.com/ros2/rcpputils/issues/139>)
* Improve rcppmath Doxygen documentation (#138 <https://github.com/ros2/rcpputils/issues/138>)
* Improve documentation of utilities in docs/FEATURES.md (#137 <https://github.com/ros2/rcpputils/issues/137>)
* Include rcppmath utilities in docs/FEATURES.md (#136 <https://github.com/ros2/rcpputils/issues/136>)
* Fix IllegalStateException reference in FEATURES (#135 <https://github.com/ros2/rcpputils/issues/135>)
* migrate rolling mean from ros2_controllers to rcppmath (#133 <https://github.com/ros2/rcpputils/issues/133>)
* Update includes after rcutils/get_env.h deprecation (#132 <https://github.com/ros2/rcpputils/issues/132>)
* Contributors: Abrar Rahman Protyasha, Barry Xu, Christophe Bedard, Karsten Knese, Octogonapus