docs(scully): fix link to CONTRIBUTING.md file (#135)

Author: Villanuevand

docs/scully.md

@@ -20,6 +20,6 @@ Visit one of the following topics:
 - [Working with Plugins](plugins.md)
 - [Code of Conduct](CODE_OF_CONDUCT.md)
 - [Issues](issues.md)
-- [Contribution Guideline](CONTRIBUTING.md)
+- [Contribution Guideline](../CONTRIBUTING.md)
 
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