feat(radio-group): add custom-class prop support (#5798)

Author: uxuip

packages/radio-group/index.wxml

@@ -1,5 +1,5 @@
 <wxs src="../wxs/utils.wxs" module="utils" />
 
-<view class="{{ utils.bem('radio-group', [direction]) }}">
+<view class="{{ utils.bem('radio-group', [direction]) }} custom-class">
   <slot></slot>
 </view>