支持离线下载m3u8链接为视频，而不是ts列表

### Please make sure of the following things

- [x] I have read the [documentation](https://alist.nn.ci).
- [ ] I'm sure there are no duplicate issues or discussions.
- [x] I'm sure this feature is not implemented.
- [x] I'm sure it's a reasonable and popular requirement.

### Description of the feature / 需求描述

离线下载m3u8链接时只能获取ts列表，不能解析为mp4文件

### Suggested solution / 实现思路

若离线下载识别为.m3u8文件
通过下载ts片段，并合并处理ts为视频文件后
上传到目标目录

谢谢

### Additional context / 附件

_No response_