docs: case-sensitivity of readme paths

docs/pyproject.md

@@ -114,6 +114,12 @@ The file(s) can be of any format, but if you intend to publish to PyPI keep the
 https://packaging.python.org/en/latest/guides/making-a-pypi-friendly-readme/) in
 mind. README paths are implicitly relative to `pyproject.toml`.
 
+{{% note %}}
+Whether paths are case-sensitive follows platform defaults, but it is recommended to keep cases.
+
+To be specific, you can set `readme = "rEaDmE.mD"` for `README.md` on macOS and Windows, but Linux users can't `poetry install` after cloning your repo. This is because macOS and Windows are case-insensitive and case-preserving.
+{{% /note %}}
+
 The contents of the README file(s) are used to populate the [Description
 field](https://packaging.python.org/en/latest/specifications/core-metadata/#description-optional)
 of your distribution's metadata (similar to `long_description` in setuptools).