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

Allows fields that are arrays of strings to be passed to `<select multiple>`
inputs.
However, I'd like to see ` raise Formulaic::InputNotFound.new(%[Unable to find input "#{label}".])` as in StringInput, rather than letting Capybara raise something, so that we have parity with that interface. Probably a good thing to do for all inputs.

Best way I can think to do it would be with `rescue` in the each. Thoughts?