fixes:

- Fix enum graphql representation (@joycex99)
- Fix construction of list types with already-realized types (#173, #166)

features:
- Codegen now accepts __typename selection as __typename__
- Allow __typename auto-selection
- Fragments and InlineFragments now support __fields__() (#71)
- sort enum doctype, keeping docs stable (@MyrikLD)

refactor & cleanup by @yezz123