1. 桌面端也支持在阅读页保存单张图片了，可在下载设置中配置保存路径
2. 优化本地画廊扫描
3. 移除桌面端阅读页ctrl键操作
4. 修复重新下载图片时的显示bug

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1. Support saving single image in reading page on desktop platform too. You can configure the save path in download setting.
2. Optimize local gallery scan.
3. Remove ctrl key operation in reading page on desktop platform.
4. Fix bug with re-downloading images.