fix: 修复 step 的 description 插槽不显示的bug

Author: YILS-LIN

src/uni_modules/wot-design-uni/components/wd-step/wd-step.vue

@@ -25,7 +25,7 @@
         <text v-else>{{ currentTitle }}</text>
       </view>
       <view v-if="$slots.description || description" class="wd-step__description">
-        <slot v-if="$slots.description" />
+        <slot v-if="$slots.description" name="description"/>
         <text v-else>{{ description }}</text>
       </view>
     </view>