Allow loading WebAssembly scripts when in node environment

When running Babylon.js in Node.js it is not enough to load the wasm, as it is required to use Node.js’ WebAssembly runtime to parse the file (https://nodejs.dev/en/learn/nodejs-with-webassembly/).
We will need to find a clean way to introduce file loading in different environments.

See discussion here - ImportAsyncMesh on server side without scene - #39 by bghgary

*Ported From GitHub