n-select: open the menu whenever it receives focus prop

[vonWolfehaus]

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

Use case: tabbing into it will focus it but ideally the menu would open and allow for keyboard input. Currently, it only glows and does not open the menu unless you press enter. The focus api method does not work, nor does simulating a keyboard event on it.

Expected API (期望的 API)

A new prop on the component called open-on-focus or similar that will open the select menu when the user tabs into the select component.