Update visitors.yml

Author: wangc168

_data/members/visitors.yml

@@ -1,3 +1,8 @@
+- name: "[Changchang Sun](https://scholar.google.com/citations?user=bCxWjjYAAAAJ&hl=en) (Visiting)"
+  info: Ph.D. student, Department of Computer Science, University of Illinois Chicago 
+  visiting: Aug. 2023 - May. 2025
+  research:
+
 - name: Yuhao Sun (remote)
   info: Graduate student, University of Science and Technology of China
   visiting: May. 2024 - Feb. 2025