Improve String Enum handling for additional use cases to ensure resul…

…ting Enums are properly formed (e.g. no unnecessary underscores being inserted in various cases). And some code naming improvements, and cleanup. Added greater Unit Test coverage for Enum parsing (serialization & deserialization).

- Improve configuration support for Defeault Json Processing now with…

… Enum Flags to make enabling/disabling the GraphQL Json Defaults much easier.

- Update README with info on the improved configuration support of the default Json processing features.

Merge branch 'main' of https://github.com/cajuncoding/FlurlGraphQL

Fix bug resulting in incorrect Exceptions when automatically enumerat…

…ing (as IAsyncEnumerable) Connection Pages when a request returns with no results (NextPage = false & EndCursor = null).

Fix csproj xml markup

Merge branch 'main' of https://github.com/cajuncoding/FlurlGraphQL

Update README.md

Fix LInk