Fallback to `select` if array of `checkboxes` fail

Allows fields that are arrays of strings to be passed to `<select multiple>`
inputs.
When trying to call `has_selector?("select[multiple]", label: label)`, the failure reads

```
invalid keys :label, should be one of :count, :minimum, :maximum, :between, :text, :visible, :exact, :match, :wait
```

I'm not sure how to find the `select` with both `multiple` and the corresponding `label`