Fix position calculations for 'vertical' mode

[mrkosima]

This PR fixes handle's position calculations for vertical mode.

[ljharb]

Thanks! Could you add a regression test that would have caught this?

[mrkosima]

I'm going to provide new PR with fixing vertical slider in storybook soon.
And will put a test for this case in it.

Can we merge this PR now and release a package, because the fix is obvious and very important for my current project?

[ljharb]

I’d prefer not to merge a fix without a regression test in the same PR.

It may be obvious looking at the diff, but it was non-obvious enough to be missed previously.

[mrkosima]

@ljharb , I've added tests, check please.

[dperyel]

Would be nice to have the fix merged soon (-;

[mrkosima]

@majapw could you please check the PR?

[mrkosima]

@ljharb could you help the PR to be merged?

[ljharb]

@mrkosima the only way for this PR to be merged is to wait patiently for maja to review and merge it :-)

[majapw]

Thanks for the fix! Sorry for the long delay in reviewing!

[mrkosima]

@ljharb is it possible to make a 3.0.2 release with this fix?

[ljharb]

@mrkosima not sure why you're pinging me; i'm sure @majapw will cut a release as soon as she has time.

[majapw]

Released! I will do better next time at quick turnaround. :)