Show error codes from mypy runs

Now it prints something like `[arg-type]` when it errors, so you can add
`# type: ignore[arg-type]` and be specific
about the error you are silencing

pyproject.toml

@@ -5,8 +5,9 @@ requires = ["setuptools",
 
 [tool.mypy]
 plugins = "numpy.typing.mypy_plugin"
-ignore_missing_imports = true
 files = "dedupe"
+show_error_codes = true
+ignore_missing_imports = true
 check_untyped_defs = true
 
 [tool.pytest.ini_options]