Add Knights Puzzle to interactive index

Ensure the Knights Puzzle is listed on the interactive index page.

src/components/InteractiveIndex.tsx

@@ -81,6 +81,15 @@ const allInteractives: Interactive[] = [
     path: '/northcotts-game',
     theme: 'Games',
     dateAdded: '2024-03-15'
+  },
+  {
+    id: 'knights-puzzle',
+    title: 'Knights Exchange Puzzle',
+    description: 'A classic chess puzzle where you must exchange the positions of white and black knights using legal knight moves.',
+    tags: ['chess', 'knights', 'puzzle', 'logic', 'strategy'],
+    path: '/knights-puzzle',
+    theme: 'Puzzles',
+    dateAdded: '2024-07-21'
   }
 ];