Make the unadorned type non-null?

_Edited in March 2025 to explicitly mention the unadorned type_

This is a follow up from #63.

GraphQL best practices are currently to [use nullable types by default](https://graphql.org/learn/best-practices/#nullability).

This is reflected in the syntax by the fact that `String` is a nullable type. That is in contrast with languages like `Swift` and `Kotlin` where `String` is non-nullable and the nullable type has a `?` modifier: `String?`.

With all the work going on in the [nullability working group](https://github.com/graphql/nullability-wg) and the advent of [semantic non null](https://github.com/captbaritone/awesome-semantic-nullability) types, feels like now is a good time to revisit. Should the unadorned type be non-null?

This issue is for gathering community feedback and use cases. Would you rather keep the current unadorned type nullable by default? Or change it to non null by default?