Prepare a test doc folder for 'csintro' updates

[ganicke]

Added a new ./test docs folder for testing course updates for csintro.

This will path at: http://makecode.microbit.org/test/courses/csintro

Note: Pages are path prefixed at ./test/ and will need to be rolled back when merged into the ./courses folder. New images are staged in ./test/static as well.

[Jaqster]

Thanks Galen!