message: [Improvement] Field: support native events
diff: <textarea
  v-if="type === 'textarea'"
  v-bind="$attrs"
  + v-on="listeners"
  ref="textarea"
  class="van-field__control"
  :value="value"
  - @input="onInput"
  - @focus="$emit('focus')"
  - @blur="$emit('blur')"
  />
  <input
  v-else
  v-bind="$attrs"
  + v-on="listeners"
  class="van-field__control"
  :type="type"
  :value="value"
  - @keypress="onKeypress"
  - @input="onInput"
  - @focus="$emit('focus')"
  - @blur="$emit('blur')"
  />
  <div
  v-if="hasIcon"
  @@ -98,6 +93,14 @@ export default create({
  computed: {
  hasIcon() {
  return this.$slots.icon || this.icon;
  + },
  +
  + listeners() {
  + return {
  + ...this.$listeners,
  + input: this.onInput,
  + keypress: this.onKeypress
  + };
  }
  },
  @@ -120,6 +123,7 @@ export default create({
  event.preventDefault();
  }
  }
  + this.$emit('keypress', event);
  },
  adjustSize() {
  