[new feature] DropdownItem: add title-class prop

docs/markdown/changelog.zh-CN.md

@@ -6,6 +6,10 @@
 
 - 新增`lock-scroll`属性
 
+##### DropdownItem
+
+- 新增`title-class`属性
+
 ##### Picker
 
 - 支持惯性滚动

packages/dropdown-item/index.js

@@ -13,7 +13,8 @@ export default sfc({
     value: null,
     title: String,
     options: Array,
-    disabled: Boolean
+    disabled: Boolean,
+    titleClass: String
   },
 
   data() {

packages/dropdown-menu/en-US.md

@@ -95,6 +95,7 @@ export default {
 | title | Item title | `String` | Text of selected option |
 | options | Options | `Array` | `[]` |
 | disabled | Whether to disable dropdown item | `Boolean` | `false` |
+| title-class | Title class | `String` | - |
 
 ### DropdownItem Events
 

packages/dropdown-menu/index.js

@@ -69,7 +69,7 @@ export default sfc({
         }}
       >
         <span
-          class={bem('title', { active: item.show })}
+          class={[bem('title', { active: item.show }), item.titleClass]}
           style={{ color: item.show ? this.activeColor : '' }}
         >
           {item.displayTitle}

packages/dropdown-menu/zh-CN.md

@@ -106,6 +106,7 @@ export default {
 | title | 菜单项标题 | `String` | 当前选中项文字 | - |
 | options | 选项数组 | `Array` | `[]` | - |
 | disabled | 是否禁用菜单 | `Boolean` | `false` | - |
+| title-class | 标题额外类名 | `String` | - | - |
 
 ### DropdownItem Events