Add AVIF support

[ironprogrammer]

Enhancement description

Because WordPress can support AVIF, it would be terrific if Playground could do the same when running GD in PHP 8.1 and up. Possible use cases include media plugin testing, having a sandbox to tinker with migrating a site's default from JPEG to AVIF, or testing WP core media handling directly.

Here's a link to test Playground with the Modern Image Formats plugin. The plugin checks if AVIF is supported, but you can also verify in Site Health's Info > Media Handling section.