Add mypy for static type checks

Makefile

@@ -7,6 +7,7 @@ help:
 	@echo "  doc        build the documentation"
 	@echo "  format     run ruff to automatically format the code"
 	@echo "  check      run ruff to check code style and quality"
+	@echo "  typecheck  run mypy for static type check"
 	@echo "  clean      clean up build and generated files"
 	@echo "  dist-clean clean up egg-info files"
 	@echo ""
@@ -28,6 +29,9 @@ check:
 	ruff check .
 	ruff format --check .
 
+typecheck:
+	mypy HinetPy
+
 clean:
 	find . -name "*.pyc" -exec rm -v {} \;
 	find . -name "*.mo" -exec rm -v {} \;

requirements-dev.txt

@@ -11,3 +11,6 @@ ruff
 sphinx
 sphinx-intl
 sphinx_rtd_theme
+# Dev dependencies for static type checks
+mypy
+types-requests