Accessibility testing npm package

[lilyhuang-github]

Starchart should be accessible and I think that's something that we can work towards.
We can add some automated testing, though automated testing doesn't catch all issues with accessibility which is why I did a bit of manual testing try to catch some issues but I ran into a bit of issue so I'm focusing a bit on the automated testing that can be done.

We can add Vitest-axe which is suppoed to be a vitest matcher for axe-core which is meant to do automated testing for accessibility. Though it can give false positives.

There are other options with upsides and downsides but axe is the more popular one.

[lilyhuang-github]

I tried to do some manual testing with checking the contrast and just using a keyboard and there weren't anything major.

I also tried doing some testing with the Windows screen reader but it was a bit hard to discern between there being an issue with the site and my user error, or potentially an issue with my screen reader since different issues might arise with different screen readers.