Issue #5036 -> Click on nav bar goes to top level doc

Closes issue #5036

This commit redirects the reader to top level doc upon clicking
on a main nav. menu item (eg. Installation [click] -> Mac OS X)

Docker-DCO-1.1-Signed-off-by: O.S. Tezer <ostezer@gmail.com> (github: ostezer)
Merge pull request #6459 from ostezer/issue-5036-main-nav-top-level-click

Issue #5036 -> Click on nav bar goes to top level doc