Add 25/75 grid split support to top navigation

[bartaz]

Done

Adds p-navigation__row--25-75 variant that aligns top navigation items with 25/75 grid split of the content below it.

Fixes https://warthogs.atlassian.net/browse/WD-8284

QA

• Open demo
• Open new navigation example: https://vanilla-framework-4960.demos.haus/docs/examples/patterns/navigation/default
• Make sure that on large screens top nav items align with grid content below it
• Make sure it renders fine on smaller screen sizes (mobile nav works correctly)
• Review other nav examples updated to new nav layout
  • https://vanilla-framework-4960.demos.haus/docs/examples/patterns/navigation/dropdown-dark
  • https://vanilla-framework-4960.demos.haus/docs/examples/patterns/navigation/search-dark
  • https://vanilla-framework-4960.demos.haus/docs/examples/patterns/navigation/sliding-dark
  • Make sure they work as expected in desktop and mobile view
• Review updated documentation:
  • A bit refreshed docs page: https://vanilla-framework-4960.demos.haus/docs/patterns/navigation
  • Make sure new navigation layout works well on Vanilla home page: https://vanilla-framework-4960.demos.haus/

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-4960.demos.haus

[lyubomir-popov]

looks good thanks @bartaz

[chillkang]

LGTM👍