docs: updated contributing link on the README

Resolves an lint issue in the docs pipeline.

https://github.com/open-feature/openfeature.dev/actions/runs/15387227215/job/43288342049?pr=1174

Signed-off-by: Michael Beemer <[email protected]>

Author: beeme1mr

README.md

@@ -97,7 +97,7 @@ The [`samples/`](./samples) folder contains example applications demonstrating h
    dotnet run
    ```
 
-Want to contribute a new sample? See our [CONTRIBUTING](#-contributing) guide!
+Want to contribute a new sample? See our [CONTRIBUTING](CONTRIBUTING.md) guide!
 
 ## 🌟 Features