Introduce GraphQL Validator #236
Description
When working with GraphQL documents, it's essential to ensure that the structure conforms to the format according to the IntrospectionQuery to prevent inconsistencies and improve compatibility with various tools and libraries.
Proposed solution
Implement GraphQL Validator for the GraphQL.Document based on the Current working draft of GraphQL specification
Expected results
GraphQL Validator is able to validate and report structural errors of the GraphQL introspection documents