Update courses.yaml (#548)

Added a course by Jun Li in Dayton.

data/courses.yaml

@@ -131,6 +131,16 @@
     We spent a little more than half the semester working through most of
     Mathematics in Lean with weekly homework assignments.
     Students have to do a small independent project at the halfway point, and a larger one at the end.
+    year: 2023
+- name: Set Theory and Logic with Lean
+  instructor: Jun Li
+  institution: University of Dayton, USA
+  website: https://lijungeometry.github.io/342.html
+  lean_version: 3
+  tags: ['English', 'intro to proof', 'logic']
+  summary: >
+    The aim of the course is to learn some set theory and logic with Lean 3.   We met twice a week, discussed upcoming topics and
+    started to work on   exercises in class. There is also a project done with LEAN together with a poster session in Stander Symposium.
   year: 2023
 - name: Démontrer avec un ordinateur
   instructor: Riccardo Brasca and Antoine Chambert-Loir