add project 3

Author: eisuke0912

_toc.yml

@@ -3,4 +3,5 @@ root: index.md
 chapters:
   - file: lecture_16_example.ipynb
   - file: project 1.ipynb
-  - file: project 2.ipynb
+  - file: project 2.ipynb
+  - file: project 3.ipynb