add support for multiple types

### What is the problem / feature ?

Keywords like `minimum` which are invalid if the type is declared as something non numeric, were not validating correctly if the declaration for `type` was an array of types.

### How did it get fixed / implemented ?

Adjusted the logic so that it checked if at least one of the required types is in the declared types.

### How can someone test / see it ?

Try validating this schema and see it validates

```js
{
  'type': ['string', 'integer'],
  'minimum': 0,
}
```

*Here is a cute animal picture for your troubles...*

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