Docs: Document UNCLOSEAI_FLOATING_BUTTON in index.html and demo.html

Updated index.html to correctly show the script tag for disabling the floating button. Also added the same documentation to demo.html for consistency.

demo.html

@@ -36,6 +36,9 @@
         
         // Disable custom styling for uncloseai.js - use PicoCSS instead
         window.UNCLOSEAI_CUSTOM_STYLING = false;
+
+        // Disable the floating button
+        window.UNCLOSEAI_FLOATING_BUTTON = false;
     </script>
 
     <script src="https://uncloseai.com/uncloseai.js" type="module"></script>

index.html

@@ -90,7 +90,7 @@
         
         <p>To disable the floating button (if you only want the API functions):</p>
         <pre><code class="javascript">&lt;script&gt;
-    
+    window.UNCLOSEAI_FLOATING_BUTTON = false;
 &lt;/script&gt;</code></pre>
         
         <h4>Class-Based Integration</h4>