Missing Dependencies

[jmz3]

Hi,

I was trying to build this repo according to the instructions provided. I encountered two problems during colcon build.

• Problem: CMake cannot find SWIG
  • Solution: sudo apt-get install swig
• Problem: CMake cannot find crtk_msgs
  • Solution: download the ros2_crtk_msgs and put it into the same dir

For problem 1, I think it's better to include it into the dependencies, or, at least, mark it in the README.

For problem 2, I don't see the reason. I see crtk_msgs has already been listed as one of the dependencies in the .repo file. But it turns out that vcs didn't install this package accordingly.

I could create a pull request to add these two notes to the README, if you agree.

Thank you!

[jmz3]

Just checked sawUniversalRobotROS2 and I realize that the installation guide for that repo contains all the missing dependencies. Perhaps adding those lines to this repo could fix the issues.