add user_name slash prompt template

src/lib/components/chat/MessageInput/Commands/Prompts.svelte

@@ -1,5 +1,5 @@
 <script lang="ts">
-	import { prompts } from '$lib/stores';
+	import { prompts, user } from '$lib/stores';
 	import {
 		findWordIndices,
 		getUserPosition,
@@ -78,6 +78,12 @@
 			text = text.replaceAll('{{USER_LOCATION}}', String(location));
 		}
 
+		if (command.content.includes('{{USER_NAME}}')) {
+			console.log($user);
+			const name = $user.name || 'User';
+			text = text.replaceAll('{{USER_NAME}}', name);
+		}
+
 		if (command.content.includes('{{USER_LANGUAGE}}')) {
 			const language = localStorage.getItem('locale') || 'en-US';
 			text = text.replaceAll('{{USER_LANGUAGE}}', language);