Replace APNG images on docsite with another format of animated image or video

[dphfox]

Currently, on pages such as Tweens and Springs, we have animated graphics in the APNG format. This format was chosen for its lossless quality and ease of use.

However, Chromium based browsers do not render APNG at 60 frames per second (this is not an issue on Firefox) so it might perhaps be worth looking into other file formats that may suffice here. An image format would be most ideal due to theme awareness, but if a video format is deemed desirable then we can always make adjustments to the FusionDoc theme.

[dphfox]

This could be due to https://learn.microsoft.com/en-gb/archive/blogs/ieinternals/trivia-animated-gif-timing

We should test to see if WebP and AVIF (no FF support) have the same problems; https://developer.mozilla.org/en-US/docs/Web/Media/Formats/Image_types