docs: Add note about toolchain issue under native Windows (pola-rs#13590

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docs/development/contributing/index.md

@@ -46,6 +46,7 @@ Polars development flow relies on both Rust and Python, which means setting up y
 If you run into problems, please contact us on [Discord](https://discord.gg/4UfP5cfBE7).
 
 _Note that if you are a Windows user, the steps below might not work as expected; try developing using [WSL](https://learn.microsoft.com/en-us/windows/wsl/install)._
+_Under native Windows, you may have to manually copy the contents of `toolchain.toml` to `py-polars/toolchain.toml`, as Git for Windows may not correctly handle symbolic links._
 
 Start by [forking](https://docs.github.com/en/get-started/quickstart/fork-a-repo) the Polars repository, then clone your forked repository using `git`: