Adds front matter for Gitaly to some docs

doc/administration/gitaly/index.md

+---
+stage: Create
+group: Gitaly
+info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#designated-technical-writers
+type: reference
+---
+
 # Gitaly
 
 [Gitaly](https://gitlab.com/gitlab-org/gitaly) is the service that

doc/administration/gitaly/praefect.md

 ---
+stage: Create
+group: Gitaly
+info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#designated-technical-writers
 type: reference
 ---
 

doc/administration/gitaly/reference.md

 ---
+stage: Create
+group: Gitaly
+info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#designated-technical-writers
 type: reference
 ---
 

doc/administration/high_availability/gitaly.md

 ---
+stage: Create
+group: Gitaly
+info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#designated-technical-writers
 type: reference
 ---
 

doc/user/project/repository/reducing_the_repo_size_using_git.md

 ---
+stage: Create
+group: Gitaly
+info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#designated-technical-writers
 type: howto
 ---