Enable strict mypy checking in pyproject.toml

Added new settings under `[tool.mypy]` in the `pyproject.toml` file to enable strict type checking. These changes will now warn of unreachable code, show pretty output, column numbers, error codes, and error context to improve development productivity and code health.

pyproject.toml

@@ -126,6 +126,14 @@ exclude_also = [
     "if TYPE_CHECKING:",
 ]
 
+[tool.mypy]
+strict = true
+warn_unreachable = true
+pretty = true
+show_column_numbers = true
+show_error_codes = true
+show_error_context = true
+
 [build-system]
 requires = ["poetry-core", "fastentrypoints"]
 build-backend = "poetry.core.masonry.api"