[new feature] Toast: add icon prop (#3485)

packages/toast/en-US.md

@@ -32,6 +32,20 @@ Toast.success('Success');
 Toast.fail('Fail');
 ```
 
+### Custom Icon
+
+```js
+Toast({
+  text: 'Custom Icon',
+  icon: 'like-o'
+});
+
+Toast({
+  text: 'Custom Image',
+  icon: 'https://img.yzcdn.cn/vant/logo.png'
+});
+```
+
 ### Advanced Usage
 
 ```javascript
@@ -102,6 +116,7 @@ toast2.clear();
 | type | Can be set to `loading` `success` `fail` `html` | `String` | `text` |
 | position | Can be set to `top` `middle` `bottom` | `String` | `middle` |
 | message | Message | `String` | `''` |
+| icon | Custom icon | `String` | - |
 | mask | Whether to show mask | `Boolean` | `false` |
 | forbidClick | Whether to forbid click background | `Boolean` | `false` |
 | loadingType | Loading icon type, can be set to `spinner` | `String` | `circular` |