[scroll-animations-1] Add examples

[bramus]

Add some examples to the scroll-animations-1 spec.

[bramus]

I believe this PR is ready for review.

One thing I struggled with is there to place the examples for animation-range. I chose not to put them under Appendix A because the entire section is marked as “This section should move to CSS-ANIMATIONS-2 and WEB-ANIMATIONS-2.”.

If I were an author, I would like to see the examples that use animation-range with scroll-driven animations in the scroll-animations-1 spec. Because of that, I have put the examples under the https://drafts.csswg.org/scroll-animations-1/#scroll-driven-attachment section which mentions restricting the active interval.

As a result, though, the section itself might need some rewording / extra sentences which I can tackle later.

[svgeesus]

LGTM

[svgeesus]

As a result, though, the section itself might need some rewording / extra sentences which I can tackle later.

That should not hold up merging this PR however