Update meta data of dictionnary

[ogerfaber]

As a maintainer of https://github.com/nielk/idonttrustlikethat-fast-check I got troubles to figure out how to convert idtlt dictionary into fast-check Arbitrary.

The main reason is that idtlt.dictionary(union('Foo', 'Bar'), number) returns only meta value with number type:

{
  "meta": {
    "tag": "dictionary",
    "value": {
      "meta": {
        "tag": "number"
      }
    }
  }
}

I would expect meta data with union type described, something like:

{
  "meta": {
    "tag": "dictionary",
    "value": {
      "meta": {
        "tag": [{
          "union": [
            {
               "meta": {},
               "literal": "Foo"
             },
            {
               "meta": {},
               "literal": "Bar"
            }
          ],
         "tag": "union"
        },
        "number"]
      }
    }
  }
}

Consequently, the following validator const dict = idtlt.dictionary(idtlt.union('Foo', 'Bar'), string) will return no information about the key type 'Foo' | 'Bar' so I can't convert it correctly to fast-check arbitrary.

Do you mind if you can expose more details in the meta data ?

Here is a complete exemple: playground

[ogerfaber]

I believe the following line would resolve my issue: https://github.com/AlexGalays/idonttrustlikethat/pull/21/files#diff-8abac0f2a235a62814031a3fb26f4846ec5c12760f528e8bcc4d29778f49f982R453