Still not perfect due to usage of a static global, but this is much cleaner and more efficient thanks to proper blocking of Workers that wait for new messages instead of a manual spin-loop.
- Refactor to work around Chromium's issue with postMessage queuing. https://bugs.chromium.org/p/chromium/issues/detail?id=1075645
- Convert codec code to TypeScript.
- Make separate parallel and non-parallel builds.
- Switch to nightly Rust for OxiPNG to allow parallel builds (but also reuse it for regular builds to avoid installing two toolchains).
