added a new dependency to the list and updated ROS 2 dependencies the link

doc/BUILD.md

@@ -5,15 +5,16 @@ Quickstart
 ----------
 
 ### Steps
-First, install all ROS2 dependencies from the ROS2 Installation page: https://github.com/ros2/ros2/wiki/Linux-Development-Setup
+First, install all ROS2 dependencies from the ROS2 Installation page: https://index.ros.org/doc/ros2/Installation/Dashing/Linux-Development-Setup/
 
 Second, install the dependencies for this repository:
 ```sh
-RUN apt-get install -y \
-    libsdl-image1.2 \
-    libsdl-image1.2-dev \
-    libsdl1.2debian \
-    libsdl1.2-dev
+sudo apt-get install -y \
+	libsdl-image1.2 \
+	libsdl-image1.2-dev \
+	libsdl1.2debian \
+	libsdl1.2-dev \
+	graphicsmagick
 ```
 
 Third, ensure there are no ROS environment variables set in your terminal or `.bashrc` file before taking the steps below.*