[DrumsUI] Updater

[Firedancer]

@Ragnaroeker: I never had the variants to begin with, so there was no backup of them on my system. I was trying to download them for the first time. I worked around it by copying the Update URL in the Settings -> File Path window, pasting it into Firefox, and following the file structure to the variant zips and downloading them directly rather than through the updater.