message: docs(Icon): fix layout usage
diff: <van-tabs v-model="tab" sticky>
  <van-tab :title="t('demo')">
  <demo-block :title="t('basicUsage')">
  + <van-row>
  <van-col span="6" @click="copy(demoIcon)">
  <van-icon :name="demoIcon" />
  </van-col>
  <van-col span="6" @click="copy(demoImage)">
  <van-icon :name="demoImage" />
  </van-col>
  + </van-row>
  </demo-block>
  <demo-block :title="t('badge')">
  + <van-row>
  <van-col span="6" @click="copy(demoIcon, { dot: true })">
  <van-icon :name="demoIcon" dot />
  </van-col>
  <van-col span="6" @click="copy(demoIcon, { badge: '99+' })">
  <van-icon :name="demoIcon" badge="99+" />
  </van-col>
  + </van-row>
  </demo-block>
  <demo-block :title="t('color')">
  + <van-row>
  <van-col span="6" @click="copy(demoIcon, { color: BLUE })">
  <van-icon :name="demoIcon" :color="BLUE" />
  </van-col>
  <van-col span="6" @click="copy(demoIcon, { color: GREEN })">
  <van-icon :name="demoIcon" :color="GREEN" />
  </van-col>
  + </van-row>
  </demo-block>
  <demo-block :title="t('size')">
  + <van-row>
  <van-col span="6" @click="copy(demoIcon, { size: '40' })">
  <van-icon :name="demoIcon" size="40" />
  </van-col>
  <van-col span="6" @click="copy(demoIcon, { size: '3rem' })">
  <van-icon :name="demoIcon" size="3rem" />
  </van-col>
  + </van-row>
  </demo-block>
  </van-tab>
  <van-tab :title="t('basic')">
  + <van-row>
  <van-col
  v-for="icon in icons.basic"
  :key="icon"
  <van-icon :name="icon" />
  <span>{{ icon }}</span>
  </van-col>
  + </van-row>
  </van-tab>
  <van-tab :title="t('outline')">
  + <van-row>
  <van-col
  v-for="icon in icons.outline"
  :key="icon"
  <van-icon :name="icon" />
  <span>{{ icon }}</span>
  </van-col>
  + </van-row>
  </van-tab>
  <van-tab :title="t('filled')">
  + <van-row>
  <van-col
  v-for="icon in icons.filled"
  :key="icon"
  <van-icon :name="icon" />
  <span>{{ icon }}</span>
  </van-col>
  + </van-row>
  </van-tab>
  </van-tabs>
  </demo-section>
  