Add support for "Digital Media" album splits

"Digital Media" is a common 'disk'-splitting prefix, more so with recent "digital" music releases as physical cd's/disks aren't used. 

In particular, it is part of Lidarr's {Medium Format} tag for automatic archive sorting. So it would be good to see this reflected into Jellyfin.

I'm not familiar with the code-base, or whether a ' ' character is valid within this context.

Emby.Naming/Common/NamingOptions.cs

@@ -175,6 +175,7 @@ namespace Emby.Naming.Common
             AlbumStackingPrefixes = new[]
             {
                 "cd",
+                "digital media",
                 "disc",
                 "disk",
                 "vol",