add welcome message

Author: commit111

app/templates/index.html

@@ -201,7 +201,7 @@
             </a>
         </div>
         <h2>Ask Defang</h2>
-        <div id="chat-box" class="chat-box"></div>
+        <div id="chat-box" class="chat-box">Welcome to Ask Defang. Let's start chatting!</div>
         <input type="text" autofocus="autofocus" id="query-input" class="input-box" placeholder="Ask a question...">
         <button id="send-button" class="submit-btn">
             Send