- add graphing calculator to tools.json and sidebar.html, add screenshot

Author: TobiasMue91

data/tools.json

@@ -1560,5 +1560,16 @@
     "aiPowered": false,
     "featured": false,
     "date": "2025-05-30"
+  },
+  {
+    "id": "graphing_calculator",
+    "title": "Graphing Calculator",
+    "description": "Free online graphing calculator with interactive plotting, zoom, pan, and support for complex mathematical functions. Plot trigonometric, polynomial, exponential, and logarithmic functions instantly.",
+    "url": "tools/graphing_calculator.html",
+    "screenshot": "screenshots/screenshot_204.webp",
+    "type": "tool",
+    "aiPowered": false,
+    "featured": false,
+    "date": "2025-05-30"
   }
 ]

screenshots/screenshot_204.webp

@@ -289,6 +289,7 @@ <h2>Tools by ChatGPT</h2>
       <li><a href="/tools/pdf_splitter.html">PDF Splitter</a></li>
       <li><a href="/tools/metronome.html">Metronome</a></li>
       <li><a href="/tools/pdf_sign.html">PDF Sign Tool</a></li>
+      <li><a href="/tools/graphing_calculator.html">Graphing Calculator</a></li>
 <!-- end -->
     </ul>
   </div>