Create an X-code extension for xcode GraphQL

Since Apple started code-signing Xcode with Xcode 9, Xcode [plugins are no longer supported](https://nshipster.com/xcode-plugins/) and it's recommended to use [extensions](https://nshipster.com/xcode-source-extensions/)

There are a few small, limited purposes for which they still work, including recognizing particular file types as tied to particular languages, which is what this plugin allows Xcode to do. However given [x-code extensions](https://developer.apple.com/documentation/xcodekit/creating_a_source_editor_extension) seem to be the way forward to support iOS developers individual add-on / plugin needs, we'll consider if it's worthy to create an extension that offers similar functionality to what is available in this x-code plugin.