chore: update sponsors

Author: kamilmysliwiec

index.html

@@ -668,6 +668,7 @@ <h5>Silver sponsors</h5>
           <a href="https://handsontable.com/docs/react-data-grid/?utm_source=NestJS_homepage&utm_medium=sponsorship&utm_campaign=library_sponsorship_2024" target="_blank" rel="nofollow">
             <img src="img/logos/handsontable-logo.svg" class="silver-logo" />
           </a>
+          <a href="https://www.itflashcards.com/" target="_blank"><img src="img/logos/it_flashcards-logo.png" class="silver-logo" /></a>
         </div>
         <div class="support-section sponsor-tiles support-section--bronze">
           <h5>Sponsors / Partners</h5>