[Chapter 12 - MicroProfile GraphQL 2.0] Add new chapter about MicroProfile GraphQL 2.0 (#68)

* Add chapter on MicroProfile GraphQL 2.0

This chapter introduces MicroProfile GraphQL 2.0, covering its features, advantages over REST, and how to implement GraphQL APIs in Jakarta EE and MicroProfile applications. It includes topics such as defining endpoints, using annotations, error handling, and project dependencies.

* Apply suggestions from code review

Co-authored-by: Rüdiger zu Dohna <ruediger.dohna@codecentric.de>

* Refine text for clarity and readability in chapter12.adoc

Corrected punctuation and improved sentence structure in the introduction and various sections of the chapter.

* Enhance introduction on APIs and GraphQL benefits

Revised introduction to clarify the challenges of REST APIs and the advantages of GraphQL in addressing diverse client needs.

* Improve clarity on network overhead and GraphQL features

Revised text for clarity and improved flow regarding network overhead and composite endpoints. Enhanced explanation of the `@Source` annotation in MicroProfile GraphQL.

* Enhance documentation for GraphQL query naming

Added explanations for using @name and @description annotations in GraphQL schema. Included Maven and Gradle configurations for preserving parameter names.

* Enhance GraphQL description in chapter12.adoc

Expanded the explanation of GraphQL to include its suitability for machine-to-machine communication and the benefits of schema-first contracts.

* Refine GraphQL service description

Removed the word 'schema-first' from the description of GraphQL service contract.

* Enhance GraphQL description with introspection details

Clarified the explanation of GraphQL introspection and its similarities to OpenAPI and Swagger UI.

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Co-authored-by: Rüdiger zu Dohna <ruediger.dohna@codecentric.de>

Author: ttelang