Add CI/CD management page to VS Code section

Add navigation item to global navigation

• Link to the merge request that introduced the new page: gitlab!172917 (merged)
• Give the MR a descriptive title.
• Optional. Link to the review app showing the new page: http://main-ee-172917.docs.gitlab-review.app/ee/editor_extensions/visual_studio_code/cicd.html

Pipeline will be broken until gitlab!172917 (merged) merges.

Related:

• Related to VS Code: create CI/CD page (gitlab!172917 - merged) which introduced the page
• Related to Plan for migrating VS Code user documentation (gitlab-vscode-extension#1530 - closed)