Support Custom Spell Attack Bonus

[tmcnulty14]

When adding spells to a Magic Item, there is a field for entering a custom/override for the Spell Save DC.

It would be useful to be able to enter a custom/override for the Spell Attack Bonus instead / as well, for spells that rely on spell attacks instead.

(Alternatively, this could be calculated by subtracting 8 from the custom Spell Save DC per the standard formula)

I currently am trying to add Fire Bolt to a Magic Item and it always uses the actor's default spellcasting trait for spell attacks.

[Possible Bug] It also seems like it also might not be adding proficiency bonus to the attack bonus: the bonus is a flat +4, which equals the actor's spellcasting ability modifier, without their proficiency bonus.