Add roles to Guild Stickers

[garantiertnicht]

Custom Emojis have a role parameter which contains an array of role-ids which can use the Emoji. There are a couple of bots exposing that feature to users, allowing them to restrict their emotes to their level roles/boosters/patreons(not sure if that's okay, but I've heard it used in that way)/….

A user of my iteration for this has now asked me if it'd be possible to have the same functionality with stickers. Given that they look the same but bigger, this sounds like something that should work. Looking at #3128 and playing with curl, that doesn't seem to be the case tho.

It'd be nice if that functionality of emojis could be mirrored. The only difference I could wish for is that restricted stickers become visible as soon as the role gets added to the user, as in without reloading Discord. But even without, it'd be something I'd be willing to add to my bot.