feat(tag): support aria (#1220)

1. 针对读屏屏蔽文字标签中的装饰性icon访问。
2. 给“关闭”icon按钮添加标签“关闭”和“按钮”控件角色。

src/tag/tag.wxml

@@ -1,12 +1,14 @@
 <view class="{{className}} {{prefix}}-class" style="{{tagStyle}} {{ customStyle }}" bind:tap="handleClick">
-  <view class="{{classPrefix}}__icon">
+  <view aria-hidden="{{true}}" class="{{classPrefix}}__icon">
     <t-icon wx:if="{{icon}}" name="{{icon}}" t-class="{{prefix}}-icon" />
     <slot wx:else name="icon" />
   </view>
   <view class="{{classPrefix}}__text">
     <slot />
   </view>
   <t-icon
+    aria-role="button"
+    aria-label="关闭"
     wx:if="{{ closable }}"
     class="{{classPrefix}}__icon-close"
     t-class="{{prefix}}-icon"