Add webp support to texture loader

[hanabi1224]

Objective

• This PR adds webp image format support to TextureLoader behind an optional feature webp

Solution

• Since webp support in image crate is very limited (e.g. lack of ALPH support), it uses FFI bindings to libwebp instead.

[DJMcNab]

I think there are places where we document our features

We need to do this for this one (we should also mention that it uses native libraries, so will be more difficult to build for someone)

[hanabi1224]

@DJMcNab Thanks! Updated changelog and doc as suggested.

[MinerSebas]

Thats the Changelog of the already released 0.5
0.6 does not have a Changelog yet.

[hanabi1224]

fixed.

[mockersf]

Didn't find an easy answer with a quick read, is the link to libwebp static or dynamic?

• if dynamic, it will need player to have libwebp built on their system for this feature
• if static, released Bevy game with this feature will need to include https://chromium.googlesource.com/webm/libwebp/+/refs/heads/main/COPYING which is not obvious or easy to find

[hanabi1224]

@mockersf It's statically linked, regarding license, could you please point me to where I should put up a notice, code doc or feature doc? Personally, I feel it belongs to a more detailed license section in readme.md

btw, libwebp has a github mirror repo

[mockersf]

we don't have a good place yet for that, I guess for now mentioning this in #1885 when it gets merged should be enough

[inodentry]

So, this PR is stale ... but here is what could happen given the status in current bevy.

From looking at the source code, I see that we are enumerating WebP (incl many others) in enum ImageFormat: https://github.com/bevyengine/bevy/blob/main/crates/bevy_render/src/texture/image.rs#L31

However, there is no actual asset loader enablement for it (and a few of the other formats listed there btw).

It is lacking here: https://github.com/bevyengine/bevy/blob/main/crates/bevy_render/src/texture/image_texture_loader.rs#L20
and here: https://github.com/bevyengine/bevy/blob/main/crates/bevy_render/src/texture/mod.rs#L39

For anyone wanting to pick this up, you could look at the places linked above, as well as the code that was in this PR, for reference. It seems like it should be relatively straighforward to bring this up to date to current bevy.

[james7132]

This has been superceded by #8220.