Add group photo for 2025

Author: odow

_posts/2024-09-26-jump_dev_2025.md

@@ -13,6 +13,8 @@ JuMP-dev 2025 was held November 17--20, 2025 in Auckland, New Zealand.
 The workshop was organized with help from the
 [Operations Research Society of New Zealand](https://orsnz.org.nz/conf57/).
 
+<img src="/assets/jump-dev-workshops/2025/group-photo.png" alt="Photo of JuMP-dev attendees (most but not all)">
+
 ## Outline
 
 The purpose of JuMP-dev is to bring together students, researchers, and