Restrict sdist content to package source and tests

This ensure that other files in the working directory are not included
when building source distributions.

pyproject.toml

@@ -76,3 +76,6 @@ ignore = ["UP032"]
 [tool.ruff.format]
 quote-style = "single"
 docstring-code-format = true
+
+[tool.hatch.build.targets.sdist]
+only-include = ["src", "tests"]