add courses materials

mkdocs.yml

@@ -92,6 +92,7 @@ extra:
 # page tree
 nav:
     - Linux basics:
+        - Courses materials: pages/bash/bash-courses.md
         - Setup: pages/course-information/setup.md
         - Navigating files and directories: pages/bash/bash-3-navigating.md
         - Working with files and directories: pages/bash/bash-4-working_with_files_and_directories.md