Add reference to GraphQL starter

Closes gh-8026

Author: snicoll

spring-boot-starters/README.adoc

@@ -55,6 +55,9 @@ do as they were designed before this was clarified.
 | https://www.google.com/recaptcha[Google's reCAPTCHA]
 | https://github.com/mkopylec/recaptcha-spring-boot-starter
 
+| http://graphql.org/[GrahQL]
+| https://github.com/merapar/graphql-spring-boot-starter
+
 | http://www.grpc.io/[gRPC]
 | https://github.com/LogNet/grpc-spring-boot-starter