Add Marcus to team members (#16)

Co-authored-by: aburnim <aburnim@proton.me>

Author: aburnim

_data/members.yml

@@ -31,3 +31,6 @@
   - name: Stephanie Wankowicz, Ph.D.
     title: Assistant Professor - Vanderbilt, Molecular Physiology & Biophysics
     photo: /assets/images/members/Wankowicz.jpg
+  - name: Marcus Collins, Ph.D. 
+    title: Senior Machine Learning Scientist
+    photo: /assets/images/members/collins.png