fix broken link (to CONTRIBUTING.md) (#198)

Author: philipodev

README.md

@@ -742,7 +742,7 @@ A function that resets the form values to their last initialized values.
 
 ## Contributors
 
-This project exists thanks to all the people who contribute. [[Contribute](CONTRIBUTING.md)].
+This project exists thanks to all the people who contribute. [[Contribute](.github/CONTRIBUTING.md)].
 <a href="https://github.com/final-form/react-final-form/graphs/contributors"><img src="https://opencollective.com/final-form/contributors.svg?width=890" /></a>
 
 ## Backers