feat: 新增 ui-skeleton 骨架屏组件 (card / list-row / circle)

components/ui-skeleton/ui-skeleton.wxml

@@ -0,0 +1,28 @@
+<view class="skeleton {{active ? 'skeleton--active' : ''}}" wx:if="{{_minDisplayShown || !active}}">
+  <!-- card variant -->
+  <block wx:if="{{variant === 'card'}}">
+    <view class="sk-card">
+      <view class="sk-bar sk-bar--title"></view>
+      <view class="sk-bar sk-bar--body"></view>
+      <view class="sk-bar sk-bar--small"></view>
+    </view>
+  </block>
+
+  <!-- list-row variant -->
+  <block wx:elif="{{variant === 'list-row'}}">
+    <view class="sk-list" wx:for="{{count}}" wx:key="*this">
+      <view class="sk-circle"></view>
+      <view class="sk-list-text">
+        <view class="sk-bar sk-bar--title"></view>
+        <view class="sk-bar sk-bar--small"></view>
+      </view>
+    </view>
+  </block>
+
+  <!-- circle variant (timer) -->
+  <block wx:elif="{{variant === 'circle'}}">
+    <view class="sk-circle sk-circle--big">
+      <view class="sk-bar sk-bar--center"></view>
+    </view>
+  </block>
+</view>