Add emcc CMake build

[nevermoreluo]

Add CMakeLists.txt and build method in package.json

[ceifa]

What is the advantage of having a CMakeLists.txt?

[nevermoreluo]

Never mind, just another build option, in case build.sh grow bigger. If it is not necessary to add one, you can close this, sorry. :)

Before read this project, I have made cmake build for lua wasm, perhaps I should ask needed before made pull request.

[ceifa]

Actually I liked it, mostly because you made it run on docker. It can be an alternative to make the build also possible on windows. I will take a deeper look later.