[docs][workflows]: add more info & controls for Working with GIFs

[marcysutton]

Summary

Continuing on from #14529, the new page on Working with GIFs has two improvements to be made:

1. Add controls to pause the animating GIF on page load to not pose accessibility problems for users with motion sensitivity, perhaps with react-gif-player;
2. Explain the phrase "beware that flashing and autoplaying GIFs can cause accessibility problems" with a bit more detail. We could certainly mention it violates WCAG 2.2.2 for "pause, stop, hide". Some resources for reference material:
   • https://source.opennews.org/articles/motion-sick/
   • https://www.w3.org/TR/UNDERSTANDING-WCAG20/time-limits-pause.html

We need to do this as part of our own commitment to accessibility in Gatsby, but we also want to take every opportunity to teach best practices–and this is a best practice for working with animation and motion on the web.