fix: Allow z-index override for Tooltip

[frankieyan]

Short description

This allows Tooltip to have its z-index overridden, as it can end up being hidden behind elements on a higher z-index:

PR Checklist

• [ ] Added tests for bugs / new features
• [x] Updated docs (storybooks, readme)
• [ ] Executed npm run validate and made sure no errors / warnings were shown
• [x] Described changes in CHANGELOG.md
• [ ] Bumped version in package.json and package-lock.json (npm --no-git-tag-version version <major|minor|patch>) ref
• [ ] Updated all static build artifacts (npm run build-all)

Versioning

Patch

[gnapse]

@frankieyan while you're at it, this PR is a great opportunity to add a new style to tooltips that is being requested: setting a max-width for them, as requested here.

Yes, a tooltip width limit would be great. In our library we have it set to 250px. Maybe 300px works too 🤔

Do you think we can slip in that change here? It would be hardcoded in the tooltip styles. I do not think we need to give the ability to customize this via a CSS variable. But maybe we do, and you prefer to do it that way. What do you think?

[frankieyan]

while you're at it, this PR is a great opportunity to add a new style to tooltips that is being requested: setting a max-width for them, as requested here.

I don't mind doing it, but I don't think we should include it in the changes here to keep it focused. I'll create a separate PR.