fix(shiki): handle array class values when highlighting code

[dbzx10299]

What

When using Shiki with certain transformers, such as the transformerNotationDiff, child[1].class is an array with this shape:

[ 'line', 'diff', 'remove' ]

If we have a code block:

```ts {1}
const foo = 'foo' // [!code ++]
```

We will have this html output:

<span class="line,diff,add highlight"></span>

Why

[vercel]

@dbzx10299 is attempting to deploy a commit to the NuxtLabs Team on Vercel.

A member of the Team first needs to authorize it.

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commit: 8337cc9

[farnabaz]

Thanks