message: field add required prop
diff: <zan-cell
  class="zan-field"
  :title="label"
  + :required="required"
  :class="{
  'zan-field--hastextarea': type === 'textarea',
  'zan-field--nolabel': !label,
  @@ -52,6 +53,7 @@ export default {
  disabled: Boolean,
  error: Boolean,
  readonly: Boolean,
  + required: Boolean,
  maxlength: [String, Number],
  border: Boolean
  },
  