v3版本增加添加其他Alist支持

[lixplus0]

Please make sure of the following things

• [x] I have read the documentation.
• [x] 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

v2版本（2.6.4）是支持添加另一个alist地址的，不过v3似乎找不到添加其他alist的选项，希望可以添加回来。

Suggested solution / 实现思路

No response

Additional context / 附件

No response

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[DreamOfIce]

也许可以考虑通过WebDAV挂载别的alist？

[vpei]

也许可以考虑通过WebDAV挂载别的alist？ 只要对方支持就可以挂载，不过挂载后不稳定。