add instructions in README for install step to work

README.md

@@ -24,6 +24,8 @@ conda activate ros
 
 # install depenedencies
 sudo apt install ros-melodic-moveit python-rosdep
+source /opt/ros/melodic/setup.zsh
+rosdep install --from-path catkin_ws/src --ignore-src -y
 pip install -r requirements.txt
 
 # make catkin workspace