feat: accordion transition

[petermakowski]

Done

• add a transition to the accordion pattern

Fixes #4539

QA

• Open https://vanilla-framework-4542.demos.haus//docs/examples/patterns/accordion/default
• Verify the accordion works as before with the addition of having a transition on expand.

Check if PR is ready for release

If this PR contains Vanilla SCSS code changes, it should contain the following changes to make sure it's ready for the release:

• PR should have one of the following labels to automatically categorise it in release notes:
  • Feature 🎁, Breaking Change 💣, Bug 🐛, Documentation 📝, Maintenance 🔨.
• Vanilla version in package.json should be updated relative to the most recent release, following semver convention:
  • if CSS class names are not changed it can be bugfix relesase (x.x.X)
  • if CSS class names are changed/added/removed it should be minor version (x.X.0)
  • see the wiki for more details
• Any changes to component class names (new patterns, variants, removed or added features) should be listed on the what's new page.
• Documentation side navigation should be updated with the relevant labels.

Screenshots

[webteam-app]

Demo starting at https://vanilla-framework-4542.demos.haus

[fitojb]

Elegant and unique motion!

[bartaz]

Could you bump package.json version to next patch (3.6.2) with this change?

[lyubomir-popov]

+1 on the animation, nice improvement. But I have an issue with the content - it implies this is a navigation, while being marked up with paragraphs. As such, the spacing between what looks like a nested accordion is inconsistent with the spacing in e.g. the side navigation. I think the content of the example should change to actual paragraph content to avoid confusion.

[lyubomir-popov]

+1ed, we agreed to address the example content in a separate pr.

[bartaz]

LGTM, thanks!