feat: add Embla Auto Scroll plugin support with editor controls

[aadil42]

Summary

Describe the change and why it is needed.

Adds first-class support for Embla's Auto Scroll plugin so rtCarousel can create smooth, continuous scrolling carousels in addition to the existing slide-by-slide Autoplay behavior.
rtCarousel already supports many Embla predefined examples including loop, RTL, slides to scroll, drag free, alignment, y-axis, autoplay, dots, controls, counter, and progress. However, continuous scrolling via the Auto Scroll plugin was not yet supported.
The existing Autoplay feature advances one snap at a time after a delay — ideal for hero sliders and testimonials. Auto Scroll fills the gap for logo strips, partner showcases, announcement tickers, and marquee-style carousels where users expect continuous motion.

Type of change

• Bug fix
• New feature
• Enhancement/refactor
• Documentation update
• Test update
• Build/CI/tooling

Related issue(s)

Closes #146

Relates to # (if applicable)

What changed

• Installed embla-carousel-auto-scroll package and imported AutoScroll plugin in view.ts
• Added 6 new block attributes: autoScroll, autoScrollSpeed, autoScrollDirection, autoScrollStartDelay, autoScrollStopOnInteraction, autoScrollStopOnMouseEnter
• Added "Auto Scroll" inspector panel with all editor controls (toggle, speed, direction, start delay, stop on interaction, stop on mouse enter)
• Auto Scroll and Autoplay are mutually exclusive — enabling one disables the other
• Enabling "Backward" direction automatically enables Loop (required for continuous backward scrolling)
• Loop toggle is disabled when direction is Backward, with contextual help text
• Updated save.tsx to pass Auto Scroll config to frontend via data-wp-context
• Updated CarouselContext and CarouselAttributes types in types.ts
• Added unit tests for Auto Scroll context configuration in view.test.ts and edit.test.tsx

Breaking changes

Does this introduce a breaking change? If yes, describe the impact and migration path below.

• Yes — migration path:
• No

Testing

Describe how this was tested.

• Unit tests
• Manual testing
• Cross-browser testing (if UI changes)

Test details:

Screenshots / recordings

Uploading compressed Screen Recording 2026-06-06 at 7.mp4…

Checklist

• I have self-reviewed this PR
• I have added/updated tests where needed
• I have updated docs where needed
• I have checked for breaking changes