Support building for web with emscripten

[Gouellie]

Some indications on how to setup the project to compile for web with emscriptem would be appreciated.

[Peter0x44]

I don't believe this is currently supported, hence there are no instructions for it.

[JeffM2501]

Premake does not support a web build out of the box, so game-premake doesn't do it. You would use the normal makefile process for that.

[Peter0x44]

I think adding support for emscripten should be possible, I'll leave this issue open for future research.

No ETA or guarantee, obviously.