Fixed broken link to CONTRIBUTING.md

Author: zoemartin01

README.md

@@ -181,7 +181,7 @@ Plugins requests and support is available in our [Modmail Plugins Server](https:
 
 ## Contributing
 
-Contributions to Modmail are always welcome, whether it be improvements to the documentation or new functionality, please feel free to make the change. Check out our [contributing guidelines](https://github.com/kyb3r/modmail/blob/master/CONTRIBUTING.md) before you get started.
+Contributions to Modmail are always welcome, whether it be improvements to the documentation or new functionality, please feel free to make the change. Check out our [contributing guidelines](https://github.com/kyb3r/modmail/blob/master/.github/CONTRIBUTING.md) before you get started.
 
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