WebAssembly support

[syoyo]

Describe the issue

Although tinyobjloader is written in C++, people want to have performant .obj parser in non-C/C++ environment, especially on the browser(JavaScript), python, container-environment, etc.

Compiling tinyobjloader using emcc and write a binding using embind will enable portable tinyobjloader module.

For example, in Python situation, we don't need to provide prebuilt binary(through cibuildwheel) or need to build from source if tinyobjloader is provided in wasm binary. We can use wasmer-python to run wasm binary on Python: https://github.com/wasmerio/wasmer-python

Initial experiment is done in branch webassembly https://github.com/tinyobjloader/tinyobjloader/tree/webassembly