Export plotly::expect_doppelganger

Hi,

First of all, thanks for this great package.
I am creating a R package to create custom plotly plots, and would like to include unit tests within this package. In this context, I was wondering if it would be possible to export the expect_doppelganger function included within the package (or the write_plotly_svg function)?
That would greatly facilitate the testing of any R visualization package depending on plotly.
Thanks in advance!

检查 tests/testthat/helper-vdiffr.R，重点关注 expect_doppelganger 和 write_plotly_svg 以及它们当前的使用方式。确定哪个 helper 应成为包接口的一部分，将其公开给依赖它的 R 可视化包，并验证现有的绘图比较工作流仍能正常运行。