sample queries, both Query and Mutation, added

spring-boot-modules/spring-boot-libraries/README.md

@@ -15,3 +15,21 @@ The "REST With Spring" Classes: http://bit.ly/restwithspring
 - [Spring Boot and Togglz Aspect](https://www.baeldung.com/spring-togglz)
 - [Getting Started with GraphQL and Spring Boot](https://www.baeldung.com/spring-graphql)
 - [An Introduction to Kong](https://www.baeldung.com/kong)
+
+### GraphQL sample queries
+
+Query
+```shell script
+curl \
+--request POST 'localhost:8081/graphql' \
+--header 'Content-Type: application/json' \
+--data-raw '{"query":"query {\n    recentPosts(count: 2, offset: 0) {\n        id\n        title\n        author {\n            id\n            posts {\n                id\n            }\n        }\n    }\n}"}'
+```
+
+Mutation
+```shell script
+curl \
+--request POST 'localhost:8081/graphql' \
+--header 'Content-Type: application/json' \
+--data-raw '{"query":"mutation {\n    writePost(title: \"New Title\", author: \"Author2\", text: \"New Text\") {\n        id\n        category\n        author {\n            id\n            name\n        }\n    }\n}"}'
+```