fix: add compound variant array className to base when slot key is unspecified

[ali-idrizi]

Description

When having multiple slots, and not specifying the slot key in compoundVariants, like:

tv({
  base: "",
  slots: {
    title: "",
  },
  compoundVariants: [{
    class: "truncate", // not explicitly passing to a specific slot
  }]
})

Conveniently, the class truncate is added to base. However, if class is an array like:

tv({
  base: "",
  slots: {
    title: "",
  },
  compoundVariants: [{
    class: ["truncate"],
  }]
})

While one would expect the same behavior, the truncate class is not passed anywhere, even though it's type-safe. The reason is that the condition that adds the class to the base slot, only checks for typeof class === "string".

This PR adds an additional check for Array.isArray. I have modified one of the tests, so it fails without the added check. Let me know if the PR can be improved in any way.

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What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

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