chore: update .gitignore and build.gradle.kts for local server testing

- Added entries to .gitignore for local Paper test server and API documentation.
- Included the run-paper plugin in build.gradle.kts for local server execution.
- Configured runServer task with Minecraft version 1.21.4 for testing.

src/main/java/com/loki/lochat/commands/chat/LocalChatCommand.java

@@ -24,7 +24,7 @@ public class LocalChatCommand implements CommandExecutor {
     @Override
     public boolean onCommand(@NotNull CommandSender sender, @NotNull Command command, @NotNull String label, @NotNull String[] args) {
         if (!(sender instanceof Player player)) {
-            sender.sendMessage(plugin.getConfigManager().getHardcodedMessages().getPlayerOnly());
+            sender.sendMessage(plugin.getConfigManager().getMessagesConfig().getPlayerOnly());
             return true;
         }