I have just tries wasm -ing makehex when I found your project. It works great!
I found only one drawback: there are some protocols where definitions are not embed into the C file (https://github.com/probonopd/MakeHex/blob/master/EncodeIR.cpp), but require an additional IRP file. For example Sony formats.. What do you think, which one is more simple: adding the missing definitions to EncodeIR.cpp, or making these IRP files somehow available? I'm still very noob with wasm, I think I'm going to try the first version - any advice is welcomed :)