Subfolder support

[Samppady]

What feature is it?

Configuration for subfolder support in RSSHub.

What problem does this feature solve?

Enables support for subfolders in RSSHub, improving feed structure and organization for users with complex setups.

Additional description

It would be helpful if the docker-compose file allowed defining a subfolder using the BASE_URL variable.
Additionally, images like logos should work within a subfolder.

Currently, a simple fix would be to update the logo path from /logo.png to ./logo.png

This is not a duplicated feature request or new RSS proposal

• I have searched existing issues to ensure this feature has not already been requested and this is not a new RSS proposal.

[TonyRL]

Logo path is fixed, you need to reverse proxy like nginx to support subdirectory routing.