feat: Establish type compatibility with graphql

[kitten]

 Summary

When merged, this PR establishes TypeScript type compatibility between graphql and this package. This is done by adding a typings/ folder with TS files to check type compatibility. Several fixes have been made to make sure that the AST types are compatible

Set of changes

• Add missing AST schema types
• Simplify Kind and OperationTypeNode output
• Simplify NullValue | BooleanValue check
• Fix type compatibility of GraphQLError
• Fix type compatibility of parse functions