add comment for how to vendorize a library sourced from a node module

gulp.d/tasks/build.js

@@ -92,6 +92,8 @@ module.exports = (src, dest, preview) => () => {
       )
       .pipe(buffer())
       .pipe(uglify()),
+    // NOTE use this statement to bundle a JavaScript library that cannot be browserified, like jQuery
+    //vfs.src(require.resolve('<package-name-or-require-path>'), opts).pipe(concat('js/vendor/<library-name>.js')),
     vfs
       .src('css/site.css', { ...opts, sourcemaps })
       .pipe(postcss((file) => ({ plugins: postcssPlugins, options: { file } }))),