Adopt Uninst/unifiedjs UST spec?

What about for GraphQL 16 or 17, moving to a universal syntax tree spec?

https://github.com/syntax-tree/unist

cons:

It would probably *break* a lot of tooling, but most of that tooling relies on the same underlying official parser? `graphql-tag` relies on `graphql/language/parser`, for example

pros:

- better tooling interoperability for multi-language tooling
- faster development of tooling across languages
- all of the above would make adopting graphql delimited string parsing across many languages much easier... for every language that adheres to uninst (which aren't many yet)

CC @johno @wooorm