Add stage / group metadata to Editor Lite page

Per the developer, this page belongs to the Create stage and the
Editor group. This commit adds metadata to the page so it's
accounted for.

doc/development/fe_guide/editor_lite.md

 ---
-stage: none
-group: unassigned
+stage: Create
+group: Editor
 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
 ---