* add url to introductory resource * Update src/data/roadmaps/linux/content/100-navigation-basics/103-directory-hierarchy.md Co-authored-by: dsh <daniel.s.holdsworth@gmail.com> * Update src/data/roadmaps/linux/content/100-navigation-basics/103-directory-hierarchy.md --------- Co-authored-by: Kamran Ahmed <kamranahmed.se@gmail.com> Co-authored-by: dsh <daniel.s.holdsworth@gmail.com>