Add suite icon to README

[ariofrio]

Summary

• Add the Hugeicons BookBookmark02Icon above the Ribbon Suite title.
• Give mobile plugin dividers equal 33 px gaps.
• Replace the break below Plugins with a fixed-height spacer image.

Testing

• npm test
• npm run check:layout
• npm run check:ui
• npm run check:heading-icons

_{Written by Codex}