update get_champion_splash_icon

[RikiBorders]

get_champion_splash_icon has a ton of special cases.

This should be updated to take in a champ id or name, map it within some sort of json containing splash arts, and then return the full link to the splash art

[RikiBorders]

Fixed nilahs splash art.

Honestly this is at worst a minor problem and can be reworked in the future. The biggest problem is the inconsistency in splash art naming, so this can be updated sometime post-launch