PixGlide WebP encoder

libwebp 1.6.0 including SharpYUV, source commit 4fa21912338357f89e4fd51cf2368325b59e9bd9.
BSD license and patent grant: LIBWEBP-COPYING.txt and LIBWEBP-PATENTS.txt.
Emscripten 6.0.13 generated JS glue and runtime: MIT option in EMSCRIPTEN-LICENSE.txt.
Additional conservative math/allocator notices: RUNTIME-ADDITIONAL-NOTICES.txt.
Included C library/runtime notices: MUSL-COPYRIGHT.txt, COMPILER-RT-LICENSE.txt.
All notice files are distributed beside codec.mjs and codec.wasm.
Build identity, source and recipe are preserved in the product repository docs/webp-codec.