code: function packageFilter(pkg, root) {
    pkg.main = pkg.glslify || (
      path.extname(pkg.main || '') !== '.js' &&
      pkg.main
    ) || 'index.glsl'
  
    return pkg
  }
docs: find the "glslify", "main", or assume main == "index.glsl" if main is a .js file then ignore it.