Mark ophan pages as such, from https://documatt.com/sphinx-errors/1-document-isnt-included-in-any/#solution

richelbilderbeek · richelbilderbeek · commit 53507c8b9099 · 2026-03-31T12:48:43.000+02:00
diff --git a/docs/lesson_plans/README.md b/docs/lesson_plans/README.md
@@ -1,3 +1,4 @@
+(orphan)=
 ---
 tags:
   - lesson
