Add mypy configuration with stricter overrides for public modules

pyproject.toml

@@ -128,3 +128,23 @@ addopts = [
     "--cov-fail-under=95",
     "--cov-report=term-missing",
 ]
+
+[tool.mypy]
+python_version = "3.12"
+warn_unused_ignores = true
+warn_redundant_casts = true
+warn_unreachable = true
+no_implicit_optional = true
+strict_equality = true
+pretty = true
+# Default expectations for the codebase; public modules may override to be stricter.
+disallow_incomplete_defs = false
+disallow_untyped_defs = false
+
+[[tool.mypy.overrides]]
+module = [
+  "python_ntfy.client",
+  "python_ntfy.__init__",
+]
+disallow_incomplete_defs = true
+disallow_untyped_defs = true