[proposal] using `< >` instead of `()` for type parameters

Recently after reading some issues using the syntax v3, I found it's painful to see so may parens.

for example, here is a very simple type, it would be even worse for complex types

(int, Js.nullable(int)) => int

it would be much nicer to write it as

(int, Js.nullable <int>) => int

the same applies to type definitions:

type list <'a> = 
  | Nil
  | Cons of ('a * list <'a>)

The root cause is () used in too many places, I have to count the parens for complex types.
I guess it is okay to use <> in types, in expressions there may be conflicts with comparisons, in type level, should be good?

The issue proposes using angle brackets instead of parentheses for type parameters in Reason syntax, with examples for nullable types and recursive type definitions. No files, tests, or entry points are named; first review the 71-comment discussion to determine whether the proposal has a settled design, then identify the parser and syntax tests before implementation.