CONTRIBUTING.md file content doesn't match its purpose #355

It seems to me that a typical CONTRIBUTING.md file is supposed to describe how one can contribute to this project (e.g. fix a bug, add a feature...) However, now CONTRIBUTING.md is mainly talking about how to install and run use this visualizer. Also, I noticed that some issues are talking about having trouble using this visualizer. Renaming the current CONTRIBUTING.md to INSTALLING.md and having another CONTRIBUTING.md specifically focusing on how people can communicate with the leadership or help polishing the project could be more proper.