code: function setDefault (opts, key, val) {
    if (opts.schema) {
      opts.prompts = opts.schema;
      delete opts.schema;
    }
    const prompts = opts.prompts || (opts.prompts = {});
    if (!prompts[key] || typeof prompts[key] !== 'object') {
      prompts[key] = {
        'type': 'string',
        'default': val
      };
    }
    else {
      prompts[key]['default'] = val;
    }
  }
docs: Set the default value for a prompt question
  
  @param {Object} opts
  @param {String} key
  @param {String} val