Support validate on multiselect

[Whoaa512]

Is your feature request related to a problem?

I'm frustrated that I have to add manual validation after my prompt runs for multiselect prompts

Describe the solution you'd like

Support validate option on multiselect and autocompleteMultiselect

Describe alternatives you've considered

Current workaround

async function getThings(choices): Promise<string[]> {
  // prompt to ask for which images to bump
  const answers = await prompts({
    type: 'multiselect',
    name: 'things',
    message: 'Which things do you want to bump?',
    choices,
  });
  if (answers.things.length === 0) {
    return getThings(choices);
  }

  return answers.things;
}