Update _docs/concepts/build_system/index.md

Co-authored-by: FranFin <58737168+FranFin@users.noreply.github.com>

Author: pablogs9

_docs/concepts/build_system/index.md

@@ -9,7 +9,7 @@ micro-ROS provides two ways of building a micro-ROS application for embedded pla
 
 **micro_ros_setup** provides a standalone build system in the form of a ROS 2 package that can be integrated in a common ROS 2 workspace. This tool is available in the [micro-ROS/micro_ros_setup](https://github.com/micro-ROS/micro_ros_setup) repository in GitHub.
 
-The micro_ros_setup tools is in charge of generating micro-ROS images that contains micro-ROS apps for the [supported hardware](/docs/overview/hardware/) boards and [RTOS](/docs/concepts/rtos/).
+The **micro_ros_setup** tool is in charge of generating micro-ROS images that contain micro-ROS apps for the [supported hardware](/docs/overview/hardware/) boards and [RTOSes](/docs/concepts/rtos/).
 
 As the micro_ros_setup package can be installed as any other ROS 2 package its usage will be through the ROS 2 CLI tool. For example in order to install the micro-ROS build system in a ROS 2 workspace just download it and build with `colcon`: