Option or slot to change the default icon for the NSelect

[leamsigc]

This function solves the problem (这个功能解决的问题)

Some design need a c custom icon for the Select and currently is no easy way to change the icon to a custom

Expected API (期望的 API)

The best possible way will be to wrap the current icon in the name slot and set the current icon as the default
that way, if the user need to change the icon.