Enums Christmas edition: support one object type, plus strings/booleans/integers.

[cristianoc]

…to one object.
Needs some more testing, and checking that the one variant with payload has a payload which as type object, instead of just assuming it.

• @thangngoc89

This:

type payload = {
  x: int,
  y: option(string),
};

type withPayload = [
  | `a
  | [@genType.as "bRenamed"] `b
  | [@genType.as true] `True
  | [@genType.as 20] `Twenty
  | `c(payload)
];

produces:

export type payload = {readonly x: number, readonly y?: string};

export type withPayload = "a" | "bRenamed" | true | 20 | payload;

[thangngoc89]

OMG 😮 This is soo cooooool