Add support for nullable primitives

[goodoldneon]

Picking up where #312 left off.

This PR adds a normalizer that converts nullable: true primitive types into anyOf types.

[bcherny]

Thanks for the contribution! A few minor suggestions.

[bcherny]

Can you remove all of these deletes? Unclear why you need them (156 is already included in 150; 155+159+160 I'm not sure what they're here for).

[goodoldneon]

@bcherny

I think we need all of these deletes. After normalizing, we no longer want nullable, format, or type to appear in the root of the schema. That's what the anyOf is replacing.

For example, the following schema:

{
  "id": "foo",
  "type": "integer",
  "format": "int32",
  "nullable": true
}

Should be normalized to this:

 {
  "id": "foo",
  "anyOf": [
    {
      "type": "integer",
      "format": "int32"
    },
    {
      "type": "null"
    }
  ]
}

Notice how nullable is gone, and type and format have moved into the anyOf

[bcherny]

Can you rm this?

[goodoldneon]

I get a TS error without it:

Type '{ type: "null"; }' is missing the following properties from type 'LinkedJSONSchema': additionalProperties, [Parent]ts(2739)

[bcherny]

Cool! Can you find a way to fix the error? eg. to add an empty additionalProperties, and to add a Parent field?

[klarstrup]

Bump 😭

[drewcorlin1]

I'd love to be able to use this feature as well. Is there anything I can do to help this PR get merged?

[austin-garner]

Bump

[goodoldneon]

Sorry, y'all. I don't write TypeScript at my new job (unfortunately 😭) so I forgot about this PR. I just responded to a comment the maintainer had, so hopefully I'll be able to push this over the finish line soon

[lucas-inflab]

I really need to make this change, is there anything I can do such as new pull request? @bcherny

[bcherny]

Closing in favor of #522