ci: add mypy type checking to CI pipeline (#608)

- Add mypy and types-protobuf to requirements-dev.txt
- Add mypy.ini with disable_error_code for import-not-found and
  import-untyped (AppKit/Foundation/google stubs unavailable)
- Add "Run mypy" step to test.yml after pytest

Author: mkusaka

.github/workflows/test.yml

@@ -29,6 +29,10 @@ jobs:
         working-directory: api/library/python/iterm2
         run: python -m pytest tests/ -v
 
+      - name: Run mypy
+        working-directory: api/library/python/iterm2
+        run: python -m mypy iterm2/
+
   xcode-tests:
     runs-on: macos-15
 

api/library/python/iterm2/mypy.ini

@@ -0,0 +1,2 @@
+[mypy]
+disable_error_code = import-not-found, import-untyped

api/library/python/iterm2/requirements-dev.txt

@@ -2,3 +2,5 @@
 pytest>=7.0.0
 pytest-cov>=4.0.0
 pytest-asyncio>=0.21.0
+mypy>=1.0.0
+types-protobuf