Support for `anyOf` and etc.

[sananguliyev]

First thanks for the repo. It looks fantastic. I have just question whether you have a plan to cover all json schema options like anyOf and etc. E.g. current version is not able to convert this.

{
  "$schema": "http://json-schema.org/schema#",
  "type": "object",
  "properties": {
    "hi": {
      "anyOf": [
        {
          "type": [
            "integer",
            "string"
          ]
        },
        {
          "type": "array",
          "items": {
            "type": [
              "integer",
              "string"
            ]
          }
        },
        {
          "type": "object",
          "properties": {
            "a": {
              "type": "string"
            }
          },
          "required": [
            "a"
          ]
        }
      ]
    }
  },
  "required": [
    "hi"
  ]
}