Add reference to GraphQL

Author: hoijnet

src/app/docs/document-graph-api/page.md

@@ -33,3 +33,4 @@ The easiest way to get started with the document API is to use the TerminusDB cl
 * [Document Insertion Reference Guide](/docs/document-insertion/)
 * [Documents in a knowledge graph and how to use them](/docs/documents-explanation/)
 * [Immutability, version history, and revision control](/docs/immutability-explanation/)
+* [GraphQA API](/docs/how-to-query-with-graphql)