Update index.md

Author: rowlandm

intakes/index.md

@@ -3,3 +3,4 @@
 This is a list of all the projects for the previous intakes:
 - [Intake 11 - Summer 2024 / 2025 (12 projects)](11-Summer-2024-2025)
 - [Intake 12 - Semester 1 2025 (9 projects)](12-Semester-1-2025)
+- [Intake 13 - Semester 2 2025 (7 projects)](13-Semester-2-2025)