Support native BigInt in ReScript v11.1.0

[dsiu]

BigInt.t should be bigint in ReScript v11.1.0.

see: https://rescript-lang.org/blog/release-11-1-0
also: https://rescript-lang.org/docs/manual/latest/primitive-types#big-integers-experimental

rescript: [77/103] src/Extras__Unknown.cmi
FAILED: src/Extras__Unknown.cmi

  We've found a bug for you!
  /Users/dsiu/code/playground/rescript-extras/src/Extras__Unknown.resi:44:15-22

  42 │ type object
  43 │ type function
  44 │ type bigInt = BigInt.t
  45 │ type symbol = Symbol.t
  46 │ 

  This type constructor, `BigInt.t`, can't be found.
  If you wanted to write a recursive type, don't forget the `rec` in `type rec`

rescript: [93/103] tests/Extras__NonEmptyArrayTests.cmj
FAILED: cannot make progress due to previous errors.
>>>> Finish compiling (exit: 1)
error Command failed with exit code 1.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.