message: [new feature]: tabs component add swipeThreshold prop
diff: <template>
  <div class="van-tabs" :class="[`van-tabs--${type}`]">
  - <div class="van-tabs__nav-wrap" v-if="type === 'line' && tabs.length > 4">
  + <div class="van-tabs__nav-wrap" v-if="type === 'line' && tabs.length > swipeThreshold">
  <div class="van-tabs__swipe" ref="swipe">
  <div class="van-tabs__nav van-tabs__nav--line">
  <div class="van-tabs__nav-bar" :style="navBarStyle"></div>
  duration: {
  type: Number,
  default: 0.3
  + },
  + swipeThreshold: {
  + type: Number,
  + default: 4
  }
  },
  curActive() {
  /* istanbul ignore else */
  - if (this.tabs.length > 4) {
  + if (this.tabs.length > this.swipeThreshold) {
  this.doOnValueChange();
  }
  }
  this.isReady = true;
  this.initEvents();
  - if (this.tabs.length > 4) {
  + if (this.tabs.length > this.swipeThreshold) {
  this.doOnValueChange();
  }
  });
  