Add Plan categories to the Plan and track page

doc/topics/plan_and_track.md

 ---
-stage: 
-group: 
+stage: Plan
+group: Project Management
 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/#assignments
 ---
 
@@ -11,18 +11,32 @@ with milestones and track your team's time. Learn how to save time with
 quick actions, see how GitLab renders Markdown text, and learn how to
 use Git to interact with GitLab.
 
-- [Epics](../user/group/epics/index.md)
+## Basic workflow features
+
+Planning features everyone needs to use day-to-day.
+
+- [Keyboard shortcuts](../user/shortcuts.md)
+- [Markdown](../user/markdown.md)
+- [Quick actions](../user/project/quick_actions.md)
+- [To-Do lists](../user/todos.md)
+- [Using Git](../topics/git/index.md)
+
+## Team Planning
+
+Get work done as a team.
+
+- [Comments and threads](../user/discussions/index.md)
 - [Issues](../user/project/issues/index.md)
-- [Labels](../user/project/labels.md)
-- [Discussions](../user/discussions/index.md)
 - [Iterations](../user/group/iterations/index.md)
+- [Labels](../user/project/labels.md)
 - [Milestones](../user/project/milestones/index.md)
 - [Requirements](../user/project/requirements/index.md)
-- [Roadmaps](../user/group/roadmap/index.md)
 - [Time tracking](../user/project/time_tracking.md)
 - [Wikis](../user/project/wiki/index.md)
-- [Keyboard shortcuts](../user/shortcuts.md)
-- [Quick actions](../user/project/quick_actions.md)
-- [Markdown](../user/markdown.md)
-- [To-Do lists](../user/todos.md)
-- [Using Git](../topics/git/index.md)
+
+## Portfolio Management
+
+Align your work across teams.
+
+- [Epics](../user/group/epics/index.md)
+- [Roadmaps](../user/group/roadmap/index.md)