Add citation about the code in html file that produce the sidebar

Author: Jianwen0451

docs/_layouts/default.html

@@ -7,6 +7,7 @@
 
 {%- include header.html -%}
 
+<!-- The code that produces the sidebar is inspired by the solution give by ChatGPT -->
 <!-- Flex container to hold sidebar and main content -->
 <div class="content-container">
   <aside class="sidebar">