Enhancement: Allow modders to easily add new transition stickers with custom set(s)

[ChillyBeanBAM]

Issue Checklist

• I have properly named my enhancement
• I have checked the Issues/Discussions pages to see if my enhancement has already been suggested

What is your suggestion, and why should it be implemented?

I've been working on a mod lately, and when I tried to add some placeholder stickers from a custom sticker set, I noticed that, even after leaving "Tutorial" and watching the transition carefully multiple times in a row, they weren't appearing. I looked into source/funkin/ui/transition/StickerSubState.hx and noticed this on line 158:

var stickerInfo:StickerInfo = new StickerInfo('stickers-set-1');

Apparently, it only reads and uses that sticker set during the transition. I propose that the code should be updated to read any sticker set in some way, including modded ones. Thank you in advance.

[AbnormalPoof]

For now you can use JSON Patch to add new stickers to stickers-set-1 without overriding existing stickers: https://funkincrew.github.io/funkin-modding-docs/10-appending-and-merging-files/10-02-merging-files.html

Though, not many people know this, so most sticker pack mods just directly replace stickers-set-1.

[EliteMasterEric]

This feature is planned.

[AbnormalPoof]

#4003 implements this.

[Hundrec]

AbnormalPoof is on it