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.
In case the retrieved file is an image and you need the IMaterial, use AddonMaterial with the path supplied from the callback.
Downloads and saves icon of Gm_construct_Beta Steam Workshop addon.
Render Time: 42ms