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Description

The vue watch function allows an array of WatchSources to be passed as the watch source, and it then triggers on any of the items in the array changing. whenever directly passes the source to watch but the typing & subsequent callback do not support arrays.

This PR adds typing for arrays and only fires the callback if any of the array items are truthy. If none of the items in the array are truthy then it does not fire the callback.

// before
function doSomething() {
  // ...
}

whenever(valueA, doSomething)
whenever(valueB, doSomething)

// after
whenever([valueA, valueB], () => {
  // ...
})

Additional context

Should there be an option to only fire the callback if every array item is truthy?
If so, which should be the default?

There is a similar PR #5096 focused on the oldValue typing. Although my PR doesn't make the same changes, it does conflict so (presuming both PRs are accepted) it might be worth me and @VChet getting our changes together into a single PR?