index.md: Notify out of date

index.md

@@ -13,6 +13,9 @@ seo:
 {{ site.description }}
 {: .fs-6 .fw-300 }
 
+This is CSE 373 Summer 2021 at the University of Washington. Looking for [**Autumn 2021**](https://courses.cs.washington.edu/courses/cse373/21au/)?
+{: .code-example }
+
 {% assign instructors = site.staffers | where: 'role', 'Instructor' %}
 {% for staffer in instructors %}
 {{ staffer }}