Add test case for `type` = `simpleTypes[]`

[darcyparker]

When a type can be multiple simple types but not all types, the resulting interface is not correct.

See https://github.com/bcherny/json-schema-to-typescript/blob/master/dist/index.d.ts#L46
and https://spacetelescope.github.io/understanding-json-schema/reference/type.html

I observed this problem with a larger schema and created this simple test case to demonstrate:

export var schema = {
  "title": "Example Schema",
  "description": "My cool schema",
  "type": "object",
  "properties": {
    "value": {
      "type": ["number", "string"]
    },
    "anotherValue": {
      "type": ["null", "string"]
    }
  },
  "required": ["value"]
}

export var types = `/** My cool schema */
export interface ExampleSchema {
  value: number | string;
  anotherValue: null | string;
}`

I haven't had time to investigate a fix.... but could try if someone else isn't able to get to it before me.

[darcyparker]

Thanks for the quick response!