BigInt not supported but it has been since v4

```js
Node 16.0.0
Serialize-Javascript 6.0.0
Typescript 4.3.4
```

I ran into this error today, my first idea is that "BigInt" is weird because I'm using typescript? 

Example data: ``{ big: BigInt(0) }``

Error:

```js
str = JSON.stringify(obj, options.isJSON ? null : replacer, options.space);
                   ^
TypeError: Do not know how to serialize a BigInt
```