Update Suru to support hero sections with 25/75 and 50/50 main suru backgrounds

[bartaz]

Done

• Updates background of default 25/75 suru to latest version of images
• Adds p-suru--25-75 as an alias to p-suru for consistency with other variants
• Updates p-suru/p-suru--25-75 to work as a hero section container, providing correct padding and background
• Updates suru component to use new CSS variables themes for Suru backgrounds
• Adds p-suru--50-50 variant

Fixes WD-8771
Fixes WD-8772

QA

• Open demo
• Check if 25/75 suru works as expected
  • https://vanilla-framework-4985.demos.haus/docs/examples/patterns/suru/default
  • https://vanilla-framework-4985.demos.haus/docs/examples/patterns/suru/dark
• Check if 50/50 suru works as expected
  • https://vanilla-framework-4985.demos.haus/docs/examples/patterns/suru/50-50
  • https://vanilla-framework-4985.demos.haus/docs/examples/patterns/suru/50-50-dark
• Check if suru as a standalone component (without content) still works as expected
  • https://vanilla-framework-4985.demos.haus/docs/examples/patterns/suru/standalone
• Review updated documentation:
  • https://vanilla-framework-4985.demos.haus/docs/patterns/suru

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-4985.demos.haus

[britneywwc]

Looks great!