Add more demos

[majido]

We have a bunch of scattered demos for scroll timelines. Specially a few that don't use element-based offsets. I think it will be a good idea to consolidate them all here under the polyfill to showcase different features of scroll animations in one place and also allow polyfill to be exercised in different ways.

Here is the ones I know about:

• https://github.com/majido/scroll-timeline-examples (available on Glitch)

[bramus]

The past few weeks I've been playing with the ScrollTimeline, using this polyfill to cater for older browsers. I'm collecting my demos over at https://codepen.io/collection/DkdaQK

[kevers-google]

Should we add a link to the collection in the README.

[bramus]

The mentioned collection dates back to 2021. Since then, all demos have been collected on https://scroll-driven-animations.style/. I still need to add the polyfill to most of those demos, though.