Add libavif to render AVIF image

[tats-u]

Fixed by #168

https://caniuse.com/avif
microsoft/playwright#22781
https://bugs.webkit.org/show_bug.cgi?id=261368

AVIF, the next generation image format, is supported by all modern browsers. However, WebKit for Windows has not supported it yet.
It's much more popular than JPEG XL (libjxl) and should be supported by WebKit for Windows as soon as possible.

https://bugs.webkit.org/show_bug.cgi?id=268503

libavif seems to be used to render AVIF image in WebKit.

AVIF image has been adopted by more and more websites day by day because it's much superior than lossy WebP and JPEG.

[donny-dont]

Hi @tats-u and anyone else who finds this particular issue.

This repository started back in early 2018 after we decided that vcpkg was a good path forward for managing third party dependencies of WebKit for Windows. When we started vcpkg was very young and didn't have a lot of the features it now has. If we started this project today using vcpkg we would approach things much differently and this repository would just have specific overlays that we could not land in the mainline registry.

Adding an additional port here means that we need to maintain said port. The mainline registry has a port defined for libavif and its dependencies. If someone wants libavif support in a Windows WebKit build we suggest that you build that port in the mainline registry of vcpkg. You would then take the contents of the installed/<triplet> directory and place it in WebKitLibraries/win of your local checkout of WebKit.

In the future this repository may move towards using the mainline vcpkg registry with some overlays and at that time distributing libavif would be revisited.

Again at this time build libavif and add it to WebKitLibraries/win and your WebKit build will build with the ability to view AVIF files.

[tats-u]

@donny-dont If that is the case, we should mention libavif in REAME.
It's as important as libwebp and libjxl today and worth mentioned there. We should prevent innocent contributors from submitting unnecessary PRs.

[donny-dont]

@tats-u adding disclaimer in #187 how does that look to you?

[tats-u]

@donny-dont I'd like libavif to be raised as an example.

[tats-u]

I'd like README to raise the names of libraries that are as helpful as the existing ones at the last chapter.

[donny-dont]

@tats-u the repository isn't setup in a manner to help you build out libavif so I'm not going to add it to the port listing. As I noted I may rework it so it would use the registry support of vcpkg at which time it would get a listing.

Are you using the Windows WebKit port directly in a product or are you just a user of Playwright?

[tats-u]

the repository isn't setup in a manner to help you build out libavif so I'm not going to add it to the port listing.

I mean #188. We don't have to mention how to build it here, but just the existence. The lack of AVIF display functionality is not good for general-purpose Web browsers today.

Are you using the Windows WebKit port directly in a product or are you just a user of Playwright?

Latter, but I would include libavif if I developed a Webkit-based browser for Windows.