Downloads a file from the supplied addon and saves it as a .cache file in garrysmod/cache folder.
This is mostly used to download the preview image of the addon, but the game seems to also use it to download replays and saves.
Whether to uncompress the file or not, assuming it was compressed with LZMA.
Downloads and saves icon of Gm_construct_Beta Steam Workshop addon.
steamworks.FileInfo( 21197, function( result ) steamworks.Download( result.previewid, true, function( name ) print( name ) end) end)