Update README.md

Added link to CONTRIBUTING.MD

Author: retailcoder

README.md

@@ -25,7 +25,7 @@ Branch     | Description | Build Status |
  * [Attributions](https://github.com/rubberduck-vba/Rubberduck/blob/next/docs/Attributions.md)
  * [About](https://github.com/rubberduck-vba/Rubberduck/blob/next/docs/About.md)
  * [Getting Started](https://github.com/rubberduck-vba/Rubberduck/blob/next/docs/GettingStarted.md)
- * [Contributing](https://github.com/rubberduck-vba/Rubberduck/wiki/Contributing)
+ * [Contributing](https://github.com/rubberduck-vba/Rubberduck/blob/next/CONTRIBUTING.md)
 
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