Persistent Hover Accessibility Guideline

# Feature Requests

### Checklist

- [X] I've read through the [Docs](https://formidable.com/open-source/victory/docs) and [Guides](https://formidable.com/open-source/victory/guides) to make sure this functionality doesn't already exist

- [X] I've searched open issues to make sure I'm not opening a duplicate issue

### Description
The WCAG guidelines have the following criteria for hover bubbles:
https://www.w3.org/TR/WCAG21/#content-on-hover-or-focus
Relevant text quoted below:
```
Hoverable
If pointer hover can trigger the additional content, then the pointer can be moved over the additional content without the additional content disappearing;
```
This is not met by the hover tooltips provided by VictoryChart currently - when hovering over the content that pops up, the content disappears since the user is no longer hovering over the relevant point.