allow setting position of bonus chest

[VMan-2002]

ideally this would be useful for 24w14potato - but the speedrun.com categories are incomplete (not having a "main story" category)

this change would be good in preparation for that though

[tildejustin]

category creation is up to @Isntmexion
a couple people have jokingly suggested this but it's certainly borderline, would you mind making a ticket about it in javacord?