Prepare to split the plugin into a new repository, adjust README

LICENSE

README.md

catkin_ws/src/learn_environment/LICENSE

catkin_ws/src/learn_environment/README.md

...environment/developer_docs/images/plugin_with_vs_code.png

catkin_ws/src/learn_environment/tasks/GETTING_STARTED.md

...s/src/learn_environment/tasks/theoretical_introduction.md