Allow recursive types, BooleanLiteralTypeAnnotations and do not crash on function types

[vitalif]

Hi! Awesome module, thanks! The only problems I've encountered are:

• lack of BooleanLiteralTypeAnnotation support
• lack of support for recursive types
• crash (assert with null) on function types

I attempted to fix these problems, please see the PR. It probably doesn't fix the recursive type problem for parametrized types, but at least it does so for simple ones.

[vitalif]

It seems I've broken a lot :( Can you give me a hint about how to fix the recursive type issue better?

[vitalif]

Ok I've pushed new version, it still fails a lot of tests but changes are intended this time :)

[lyleunderwood]

@vitalif I just used your support for recursive types, super helpful, would love to see this merged.

@loyd This project has been working surprisingly well for my use case, but understandably it hasn't seen much maintenance for a while. Would you be interested in any help maintaining it?