className take a classnames object

classy components get a className prop by default, which accepts a string. It would be nice if it also could take a classnames object.

Instead of writing:

```ts
<Container className={classy.string(props.className, "pt-10 pb-14 px-8")}>
```

I could write:

```ts
<Container className={[props.className, "pt-10 pb-14 px-8"]}>
```