video-encoder

WebCodec is promising toolkit for precise and high-performace multi-media web apps. This project is one of series polyfilling WebCodes for older browsers.

What's provided:
* VideoEncoder/VideoFrame polyfill with XVideoEncoder/XVideoFrame, keep api almost the same
* sad/satd simd optimazation for x264 webassembly

What's still in WIP:
* aligning to WebCodec Spec
* size and performace optimazation
* easy to load