Add reference to ArangoDB starter

Closes gh-15144

spring-boot-project/spring-boot-starters/README.adoc

@@ -34,6 +34,9 @@ do as they were designed before this was clarified.
 | http://wicket.apache.org/[Apache Wicket]
 | https://github.com/MarcGiffing/wicket-spring-boot
 
+| http://arangodb.com/[ArangoDB]
+| https://github.com/arangodb/spring-boot-starter
+
 | http://www.axonframework.org/[Axon Framework]
 | https://github.com/AxonFramework/AxonFramework