chore: add mypy config

pyproject.toml

@@ -140,4 +140,21 @@ markers = [
     "issue: mark tests with current issues (deselect with '-m \"not issues\"')",
     "working: marks tests which are working",
     "fetch: marks tests which fetch data",
-]
+]
+
+[tool.mypy]
+files = ["src"]
+python_version = "3.9"
+warn_unused_configs = true
+strict = true
+show_error_codes = true
+enable_error_code = ["ignore-without-code", "redundant-expr", "truthy-bool"]
+warn_unreachable = true
+disallow_untyped_defs = false
+disallow_incomplete_defs = false
+ignore_missing_imports = true
+
+[[tool.mypy.overrides]]
+module = "antarctic_plots.*"
+disallow_untyped_defs = true
+disallow_incomplete_defs = true