[Enhancement]: Allow multi-select in the mobile app to select more than one book at once for download

[kuldan5853]

Describe the Feature/Enhancement

Right now, to download a book to your phone, you need to open it in the library view, and then select download.

I would suggest that on the library view, a long press on an audiobook opens a multi-select mode (same as the radio button in the web gui) to select multiple books, enabling a "download" button to batch queue downloads.

(This would then also apply to the downloaded content view for deletion I assume).

Why would this be helpful?

If you want to keep a big library available offline, you need to do a lot of individual clicking to download books one by one.

Future Implementation (Screenshot)

Audiobookshelf App Version

Android App - 0.9.63

Current Implementation (Screenshot)

[kuldan5853]

This also links to:
#1043
#1114

[nichwall]

Duplicate of #188

[advplyr]

renamed #188 to be more easy to find

[kuldan5853]

renamed #188 to be more easy to find

Thank you!