Accordion Side Navigation for Docs

[abhigyanghosh30]

Done

Converts side navigation into accordion

Fixes [WD-2278](https://warthogs.atlassian.net/browse/WD-2278)

QA

• Open demo
• Side navigation should have accordion
• Review updated documentation:
  • [List any updated documentation for review]

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.

Screenshots

[webteam-app]

Demo starting at https://vanilla-framework-4692.demos.haus

[bartaz]

There seem to be some issues with scrolling in side navigation now, but I guess it may not be related to this PR but some bug in side nav or accordion. I will need to debug more.

[abhigyanghosh30]

The scroll thing happened after I rebased to main. Might be an issue with interaction between the recent changes to the side nav

[bartaz]

This got reimplemented with new documentation layout in #4863. But thanks @abhigyanghosh30 for paving the path!