Add example showing how to use Slang/WASM

[aleino-nv]

This closes #5656.

[csyonghe]

showing how WebGPU applications can use the slang-wasm library to compile slang shaders at runtime to wgsl.

[aleino-nv]

Done.

[jkwak-work]

Looks good to me.

I am wondering if it will be more helpful to add some comments, because the goal of this change is to tech how to use.
But too many comments may just bloat the line count.

[jkwak-work]

is render() gets called only once?
Or does it get called every frame?

[aleino-nv]

It's just called once, since there is no animation in the example.

[aleino-nv]

Looks good to me.

I am wondering if it will be more helpful to add some comments, because the goal of this change is to tech how to use. But too many comments may just bloat the line count.

Yeah I considered it, but most of the code is WebGPU -related.
The Slang-API code is the following, which I find is quite self-explanatory:

        var module = slangSession.loadModuleFromSource(
            slangCode, "shader", '/shader.slang'
        );
        var vertexEntryPoint = module.findAndCheckEntryPoint(
            "vertexMain", slang.constants.STAGE_VERTEX
        );
        var fragmentEntryPoint = module.findAndCheckEntryPoint(
            "fragmentMain", slang.constants.STAGE_FRAGMENT
        );
        var linkedProgram = slangSession.createCompositeComponentType([
            module, vertexEntryPoint, fragmentEntryPoint
        ]).link();
        wgslShaders = {
            vertex: linkedProgram.getEntryPointCode(
                0 /* entryPointIndex */, 0 /* targetIndex */
            ),
            fragment: linkedProgram.getEntryPointCode(
                1 /* entryPointIndex */, 0 /* targetIndex */
            ),
        };