mixing spaces and tabs makes illegible md files

[fcolecumberri]

In the file https://github.com/bponsler/ros2-support/blob/master/tutorials/creating-a-mixed-cpp-and-python-package.md (but this could hapen in other files) you are mixing spaces and tabs which makes difficult to understand the filesystem layout in the md rendered version. if you see the raw version in https://raw.githubusercontent.com/bponsler/ros2-support/master/tutorials/creating-a-mixed-cpp-and-python-package.md you will notice that the filesystem layout is clear and easy to understand.