Add topics in the Runner docs to global navigation

Problem to solve

@eread described a problem to me this afternoon: pages like https://docs.gitlab.com/runner/best_practice/index.html are not included in the global navigation, which impedes SEO and makes it harder for users to discover useful items. These topics should appear in the global navigation.

Further details

Proposal

Review the instructions at https://docs.gitlab.com/ee/development/documentation/site_architecture/global_nav.html and add topics to the global navigation.

Who can address the issue

Anyone on the technical writing team.

Other links/references