Merge branch 'doc/update-grid' into 'master'

updated README of exercise-grids

See merge request !298

(cherry picked from commit 0c9e53a1)

0c236e59 Update exercise-grids README
7c1a6884 Create patch for updated exercise-grids

Co-authored-by: David Lipp <david.lipp@iws.uni-stuttgart.de>