Add validate

[Axot017]

Hello!

I would like to add library that i recently published on opam. It is a PPX deriver that generates function for validating given type based on attributes.

Here is example usage

type test_record = {
  min : string; [@min_length 2]
  max : string; [@max_length 5]
  numeric_list : (int [@less_than 10]) list; [@min_length 2] 
}
[@@deriving validate]

let example_record = { min = "ab"; max = "hello"; numeric_list = [1, 2, 3] }
let validation_result = validate_test_record example_record

Repo: https://github.com/Axot017/validate

[rizo]

Apologies for the delay. Thanks for adding this!