Add GraphQL Maven and Gradle codegen plugins (chentsulin#518)

* Add GraphQL Maven and Gradle codegen plugins

* Fix description for graphql-java-codegen plugins

Author: kobylynskyi

README.md

@@ -250,6 +250,8 @@ If you want to contribute to this list (please do), send me a pull request.
 * [schemagen-graphql](https://github.com/bpatters/schemagen-graphql) - Schema generation and execution package that turns POJO's into a GraphQL Java queryable set of objects. Enables exposing any service as a GraphQL service using Annotations.
 * [graphql-java-annotations](https://github.com/Enigmatis/graphql-java-annotations) - Provides annotations-based syntax for schema definition with GraphQL Java.
 * [graphql-java-tools](https://github.com/graphql-java-kickstart/graphql-java-tools) - Schema-first graphql-java convenience library that makes it easy to bring your own implementations as data resolvers.  Inspired by [graphql-tools](https://github.com/apollographql/graphql-tools) for JS.
+* [graphql-java-codegen-maven-plugin](https://github.com/kobylynskyi/graphql-java-codegen-maven-plugin) - Schema-first maven plugin for generating Java types and Resolver interfaces. Works perfectly in conjunction with graphql-java-tools. Inspired by [swagger-codegen-maven-plugin](https://github.com/swagger-api/swagger-codegen/tree/master/modules/swagger-codegen-maven-plugin).
+* [graphql-java-codegen-gradle-plugin](https://github.com/kobylynskyi/graphql-java-codegen-gradle-plugin) - Schema-first gradle plugin for generating Java types and Resolver interfaces. Works perfectly in conjunction with graphql-java-tools. Inspired by [gradle-swagger-generator-plugin](https://github.com/int128/gradle-swagger-generator-plugin).
 * [graphql-java-servlet](https://github.com/graphql-java-kickstart/graphql-java-servlet) - A framework-agnostic java servlet for exposing graphql-java query endpoints with GET, POST, and multipart uploads.
 * [spring-graphql-common](https://github.com/oembedler/spring-graphql-common) - Spring Framework GraphQL Library.
 * [graphql-spring-boot](https://github.com/oembedler/graphql-spring-boot) - GraphQL and GraphiQL Spring Framework Boot Starters.