message: [improvement] Field: increase clickable area of icon
diff: font-size: @field-clear-icon-size;
  }
  - &__left-icon .van-icon,
  - &__right-icon .van-icon {
  + &__left-icon,
  + &__right-icon {
  + position: relative;
  +
  + .van-icon {
  display: block;
  min-width: 1em;
  font-size: @field-icon-size;
  line-height: inherit;
  }
  + // increase clickable area size
  + &::after {
  + position: absolute;
  + top: -5px;
  + right: -5px;
  + bottom: -5px;
  + left: -5px;
  + content: '';
  + }
  + }
  +
  &__left-icon {
  margin-right: 5px;
  }
  