message: perf: disable enableObjectSlots to reduce bundle size
diff: module.exports = {
  presets: [
  - ['@vant/cli/preset', { loose: process.env.BUILD_TARGET === 'package' }],
  + [
  + '@vant/cli/preset',
  + {
  + loose: process.env.BUILD_TARGET === 'package',
  + enableObjectSlots: false,
  + },
  + ],
  ],
  };
  