add sku-header-price slot (#705)

* [new feature] add sku-header-price slot

packages/sku/Sku.vue

@@ -17,10 +17,19 @@
       <sku-header
         :sku-event-bus="skuEventBus"
         :selected-sku="selectedSku"
-        :selected-sku-comb="selectedSkuComb"
         :goods="goods"
         :sku="sku"
-      />
+      >
+        <slot
+          name="sku-header-price"
+          :price="price"
+          :selected-sku-comb="selectedSkuComb"
+        >
+          <div class="van-sku__goods-price">
+            <span class="van-sku__price-symbol">￥</span><span class="van-sku__price-num">{{ price }}</span>
+          </div>
+        </slot>
+      </sku-header>
     </slot>
     <div class="van-sku-body" :style="bodyStyle">
       <!-- sku-body-top -->
@@ -251,6 +260,14 @@ export default create({
       return null;
     },
 
+    price() {
+      if (this.selectedSkuComb) {
+        return (this.selectedSkuComb.price / 100).toFixed(2);
+      }
+      // sku.price是一个格式化好的价格区间
+      return this.sku.price;
+    },
+
     skuTree() {
       return this.sku.tree || [];
     }