Add CustomMobs plugin configuration and update command logic

Introduced a new configuration file for the CustomMobs plugin, specifying its details and commands. Updated the CommandManager to use "custommobs" instead of "fish" and added an alias "cm" for command execution.

src/main/java/com/alttd/custommobs/commands/CommandManager.java

@@ -20,7 +20,7 @@ public class CommandManager implements CommandExecutor, TabExecutor {
     private final List<SubCommand> subCommands;
 
     public CommandManager(Main main) {
-        PluginCommand command = main.getCommand("fish");
+        PluginCommand command = main.getCommand("custommobs");
         if (command == null) {
             subCommands = null;
             log.error("Unable to find transfer command.");
@@ -28,6 +28,7 @@ public class CommandManager implements CommandExecutor, TabExecutor {
         }
         command.setExecutor(this);
         command.setTabCompleter(this);
+        command.setAliases(List.of("cm"));
 
         subCommands = Arrays.asList(
                 new Spawn(main)