chore: add mypy python version intructions

Author: nullswan

README.md

@@ -8,6 +8,8 @@ Rename all `pytemplate` (including folder names) by the name of your project.
 
 Make sure you can run the `pytemplate-cli` command that should display "Hello World!"
 
+Configure your python version in the .mypy.ini, by default we uses `3.10`.
+
 ---
 
 ## Environment