Add a bulk download option for all files

[KingSupernova31]

The API currently allows you to download files by set code or date, but if I want all of them there's no easy way to do that.

[lunakv]

You can view set information about all available sets using the /metadata/{cr|mtr|ipg} endpoint, then iterate over the info from the response to get all hosted files.

Note that these endpoints are unpublished and subject to future change.

[KingSupernova31]

Fair enough. I'll leave this open in case you want to eventually add that endpoint to the docs.