chore: Add link to dashboard to get API Key

Author: greynewell

README.md

@@ -27,7 +27,7 @@ All endpoints accept a zipped repository snapshot and return graph data as JSON.
 
 ## Authentication
 
-Requests require an API key via `X-Api-Key` header.
+Requests require an API key via `X-Api-Key` header. Get your key from the [Supermodel Dashboard](https://supermodeltools.com/dashboard).
 
 ## Links