feat(leadership): add Li Ying (#113)

Author: yl25946

teams/leadership.toml

@@ -22,7 +22,8 @@ contributors = [
     "JackHurew",     # Head of Data & Analytics
     "ap-1",          # Head of DevOps
     "qianxuege",     # Tech Lead of CMU Cal
-    "xavilien",      # Tech Lead of CMU Courses
+    "xavilien",      # Tech Co-Lead of CMU Courses
+    "yl25946",       # Tech Co-Lead of CMU Courses
     "cirex-web",     # Tech Co-Lead of CMU Eats
     "laasyaaki",     # Tech Co-Lead of CMU Eats
     "luke992",       # Tech Co-Lead of CMU Maps