GITBOOK-134: Update contribution page

Author: kenrogers

contribute.md

@@ -1,5 +1,11 @@
 # Contribute
 
+### Contribute to Stacks Core
+
+There is a [detailed contribution guide](https://github.com/stacks-network/stacks-core/blob/master/CONTRIBUTING.md) that lives in the Stacks core GitHub repository that is the best place to get started contributing to Stacks.
+
+### Contribute to these Docs
+
 The Stacks docs are built using GitBook with a two-way sync with the [docs repository on GitHub](https://github.com/stacks-network/docs).
 
 Because of this two-way sync, you can contribute to the documentation in one of two ways: