New command: /cooldown or /cd

Function: Induces a cooldown on the held item (the same kind of cooldown as is already implemented in the game, for example when throwing ender pearls)

Parameters: group: sets the cooldowns group; items with the same cd group will share a cooldown

Duration: sets how long the cooldown should last (in ticks)

Why? A /cd command would be a huge addon for anyone making custom weapons/items with command/datapacks, as there is currently no good and easy way to show cooldowns of weapon right click abilities, this would fix that problem.