Support compiling to WebAssembly?

[ghost]

WebAssembly is pushed very hard and become very viral recently. Especially with the initiative like WASI (https://wasi.dev/) it's already powerful enough to be the target of many new and traditionally compiled languages, including C/C++ with the power of Emscripten.

[ghost]

What do you think about this? WebAssembly is the trend now. With your current developing LLVM backend or my proposal to ditch everything and reimplement from scratch using LLVM (#1129), it's easily possible. The key is LLVM. LLVM has everything needed for you to target WebAssembly. Please have a look at:

https://github.com/emscripten-core/emscripten

https://github.com/WebAssembly/binaryen