Image enhancements - Support toolbar custom style

[Kigoal]

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

Improve functions and enhance user experience

Expected API (期望的 API)

<n-image-group show-toolbar="custom">
  <n-space>
    <n-image
      width="100"
      src="https://07akioni.oss-cn-beijing.aliyuncs.com/07akioni.jpeg"
    />
    <n-image
      width="100"
      src="https://gw.alipayobjects.com/zos/antfincdn/aPkFc8Sj7n/method-draw-image.svg"
    />
  </n-space>
</n-image-group>

[Kigoal]

Theme: Light

Theme: Dark