custom-effect 
Adds or removes custom status effects of players and entities.
Syntax 
- custom-effect clear <entity: target> [custom_effect: string]
 Removes all custom effects or a custom effect.
- custom-effect give <entity: target> <custom_effect: string> [duration: integer]
 Gives a custom effect.
Arguments 
- <entity: target>
 Specifies the target(s).
- <custom_effect: string>
 Any custom effect registered with- customEffectRegistry.
- <duration: integer>
 Specifies the effect's duration in seconds.
