Display Slot Argument

Must be a scoreboard display slot. Returns DisplaySlot. Example:

Scoreboard scoreboardManager = Bukkit.getScoreboardManager()!!.mainScoreboard;
Objective objective = scoreboardManager.registerNewObjective(
    "health",
    Criteria.HEALTH,
    "health"
);

new StellarCommand("displaySlot")
    .addDisplaySlotArgument("slot")
    .addExecution<Player>(Player.class, context -> {
        val slot = context.getArgument<DisplaySlot>("slot");
        objective.setDisplaySlot(slot);
    });