Add /help command and various gameplay fixes

Introduce a HelpCommand (/help) and register it in SpeedHG; add its localized help text and plugin.yml entry. Prevent kit ability use while in gladiator by checking metadata in KitEventDispatcher and add a matching translation key. Early-return in KitCommand during ENDING state. Fix English message in TeamCommand and adjust spacing in LeaderboardMenu lore. Remove an unused import in SpeedHG and add necessary imports.

src/main/kotlin/club/mcscrims/speedhg/command/TeamCommand.kt

@@ -32,7 +32,7 @@ class TeamCommand : CommandExecutor, TabCompleter {
 		args: Array<out String>
 	): Boolean {
 		val player = sender as? Player ?: run {
-			sender.sendMessage("§cNur Spieler können diesen Befehl nutzen.")
+			sender.sendMessage("§cOnly players can use this command.")
 			return true
 		}