slash support in #includes

[mbredif]

Allowing slashes in the filenames of shader chunk includes would allow to use the same pattern as in C++ includes : you could scope the name of the shader by the name of the library that provides the chunk

in the custom shader:

#include <mylib/mychunk>

in the custom ShaderMaterial:

var MyShaderChunk = {};
MyShaderChunk['mylib/mychunk'] = '// some glsl code';
Object.assign(THREE.ShaderChunk, MyShaderChunk);

---

As an extension, the call to Object.assign could be wrapped in a more elegant function that optionnally prepends the path prefix :

THREE.ShaderChunk.install = function install(chunks, path) {
    if (!path) return Object.assign(this, chunks);
    Object.keys(chunks).forEach((key) => {
        this[path + key] = chunks[key];
    });
};
var MyShaderChunk = {};
MyShaderChunk.mychunk = '// some glsl code';
THREE.ShaderChunk.install(MyShaderChunk, 'mylib/');

[mrdoob]

Thanks!