To support the dark theme, we need to style the vertical cursor used with tooltips. In order to do that, we must override Victory's cursor component. <img width="779" alt="Screen Shot 2022-05-04 at 7 18 39 PM" src="https://user-images.githubusercontent.com/17481322/166840534-a19d272e-e20f-4de3-a930-10ea33f0962c.png">