[Doc] add some english documents (#220)

* [bugfix] Checkbox border render error in weixin browser

* [bugfix] TreeSelect dependency path error

* [bugfix] Swipe should clear autoplay timer when destroyed

docs/examples-docs/en-US/pull-refresh.md

@@ -0,0 +1,93 @@
+<script>
+import { Toast } from 'packages';
+
+export default {
+  data() {
+    return {
+      count: 0,
+      isLoading: false
+    }
+  },
+
+  watch: {
+    isLoading() {
+      if (this.isLoading) {
+        setTimeout(() => {
+          Toast('刷新成功');
+          this.isLoading = false;
+          this.count++;
+        }, 500);
+      }
+    }
+  },
+
+  mounted() {
+    const head = document.querySelector('.van-pull-refresh__head');
+    head.insertAdjacentHTML('afterend', '<h1 class="zan-doc-demo-block__title">PullRefresh 下拉刷新</h1>');
+  }
+}
+</script>
+
+## PullRefresh
+
+### Install
+``` javascript
+import { PullRefresh } from 'vant';
+
+Vue.component(PullRefresh.name, PullRefresh);
+```
+
+### Usage
+
+:::demo  
+```html
+<!-- 通过 v-model 控制加载状态 -->
+<van-pull-refresh v-model="isLoading">
+  <p>刷新次数: {{ count }}</p>
+</van-pull-refresh>
+```
+
+```javascript
+export default {
+  data() {
+    return {
+      count: 0,
+      isLoading: false
+    }
+  },
+
+  watch: {
+    isLoading() {
+      if (this.isLoading) {
+        setTimeout(() => {
+          Toast('刷新成功');
+          this.isLoading = false;
+          this.count++;
+        }, 500);
+      }
+    }
+  }
+}
+```
+:::
+
+### API
+
+| Attribute | Description | Type | Default | Accepted Values |
+|-----------|-----------|-----------|-------------|-------------|
+| v-model | 是否在加载中 | `Boolean` | - | - |
+| pullingText | 下拉过程中顶部文案 | `String` | `下拉即可刷新...` | - |
+| loosingText | 释放过程中顶部文案 | `String` | `释放即可刷新...` | - |
+| loadingText | 加载过程中顶部文案 | `String` | `加载中...` | - |
+| animationDuration | 动画时长 | `Number` | `300` | - |
+| headHeight | 顶部内容高度 | `Number` | `50` | - |
+
+### Slot
+
+| name | Description |
+|-----------|-----------|
+| - | 自定义内容 |
+| normal | 非下拉状态时顶部内容 |
+| pulling | 下拉过程中顶部内容 |
+| loosing | 释放过程中顶部内容 |
+| loading | 加载过程中顶部内容 |