docs(README-zh_CN.md): add bouned title explain by zh_CN (#697)

Author: ringozzt

website/docs/zh/guide/11-bounded.md

@@ -1,4 +1,6 @@
-# 11 - Dragging grid items bounded to grid container
+# 11 - 拖动栅格元素绑定到容器
+
+可以获得栅格元素的坐标与容器间的绑定关系。
 
 [查看资料](https://github.com/jbaysolutions/vue-grid-layout/blob/master/website/docs/.vuepress/components/Example11Bounded.vue)