docs(List): add PullRefresh demo (#5579)

src/list/README.md

@@ -37,7 +37,6 @@ export default {
       finished: false
     };
   },
-
   methods: {
     onLoad() {
       setTimeout(() => {
@@ -49,7 +48,7 @@ export default {
         if (this.list.length >= 40) {
           this.finished = true;
         }
-      }, 500);
+      }, 1000);
     }
   }
 }
@@ -77,7 +76,6 @@ export default {
       loading: false
     };
   },
-
   methods: {
     onLoad() {
       fetchSomeThing().catch(() => {
@@ -88,6 +86,58 @@ export default {
 }
 ```
 
+### PullRefresh
+
+```html
+<van-pull-refresh v-model="refreshing" @refresh="onRefresh">
+  <van-list
+    v-model="loading"
+    :finished="finished"
+    finished-text="Finished"
+    @load="onLoad"
+  >
+    <van-cell v-for="item in list" :key="item" :title="item" />
+  </van-list>
+</van-pull-refresh>
+```
+
+```js
+export default {
+  data() {
+    return {
+      list: [],
+      loading: false,
+      finished: false,
+      refreshing: false
+    };
+  },
+  methods: {
+    onLoad() {
+      setTimeout(() => {
+        if (this.refreshing) {
+          this.list = [];
+          this.refreshing = false;
+        }
+
+        for (let i = 0; i < 10; i++) {
+          this.list.push(this.list.length + 1);
+        }
+        this.loading = false;
+
+        if (this.list.length >= 40) {
+          this.finished = true;
+        }
+      }, 1000);
+    },
+    onRefresh() {
+      this.finished = false;
+      this.loading = true;
+      this.onLoad();
+    }
+  }
+}
+```
+
 ## API
 
 ### Props