feat: all pages can have same intro, exams guide

guide/semesters/semester3.md

@@ -1,3 +1,5 @@
+<!--@include: ../../notice.md-->
+
 # Semester 3
 Semester 3 is an interesting semester in terms of the courses, ranging from well taught (Analysis II and TI) to atrocious (NumCS).
 The same applies also to Semester 4, but the courses there are easier for many people.