🎨 Optimized gulp zip file generation (#403)

no issue

- Optimised the `gulp zip` task, so the zip file doesn't include the `assets/css` (`built` folder is used for CSS) and the `dist` folder (is used to output the zip file)

gulpfile.js

@@ -56,7 +56,12 @@ gulp.task('zip', ['css'], function() {
     var themeName = require('./package.json').name;
     var filename = themeName + '.zip';
 
-    return gulp.src(['**', '!node_modules', '!node_modules/**'])
+    return gulp.src([
+        '**',
+        '!node_modules', '!node_modules/**',
+        '!dist', '!dist/**',
+        '!assets/css', '!assets/css/**',
+    ])
         .pipe(zip(filename))
         .pipe(gulp.dest(targetDir));
 });