fixed el-alert: if using slot, icon should use 'isBigIcon' class
fixed el-alert: if using slot, icon should use 'isBigIcon' class

Kingwl/element,immissile/m-element,Kingwl/element,baiyaaaaa/element,huguangju/element,Leopoldthecoder/element-1,huguangju/element,ElemeFE/element,immissile/m-element,ElemeFE/element,Leopoldthecoder/element-1,Raganof/element,Raganof/element,baiyaaaaa/element