Support GraphQL 16

[yurchik-spb]

Are you planning to add support for GraphQL 16 schema in the code generator?
For example, I'm having trouble using the @oneOf directive in the schema GraphQL 16

input TCodeFilter @oneOf {
  status: Int
  statusExt: Int
}

Cannot load graphql schema
C:\projects\workspace\node_modules\graphql-ts-client-codegen\node_modules\graphql\validation\validate.js:107
    throw new Error(errors.map(function (error) {
          ^

Error: Unknown directive "@oneOf".
    at assertValidSDL (C:\projects\workspace\node_modules\graphql-ts-client-codegen\node_modules\graphql\validation\validate.js:107:11)
    at buildASTSchema (C:\projects\workspace\node_modules\graphql-ts-client-codegen\node_modules\graphql\utilities\buildASTSchema.js:45:34)
    at buildSchema (C:\projects\workspace\node_modules\graphql-ts-client-codegen\node_modules\graphql\utilities\buildASTSchema.js:112:10)
    at C:\projects\workspace\node_modules\graphql-ts-client-codegen\dist\SchemaLoader.js:45:44
    at Generator.next (<anonymous>)
    at fulfilled (C:\projects\workspace\node_modules\graphql-ts-client-codegen\dist\SchemaLoader.js:14:58)

[babyfish-ct]

Sorry, I'm currently mantaining a large Java project (https://github.com/babyfish-ct/jimmer) and feverishly developing its TypeScript port (https://github.com/babyfish-ct/ts-grm), so I'm really stretched thin at the moment.