web:add donate button to index page

web/templates/index.html

@@ -40,6 +40,7 @@
                         </a>
                     </div>
                     <div>
+                        <a href="https://donate.ardupilot.org" target="_blank" class="btn btn-warning rounded-pill me-1"><i class="bi bi-heart me-2"></i>Donate</a>
                         <a href="https://ardupilot.org/copter/docs/common-custom-firmware.html" class="btn btn-outline-light me-1"><i
                                 class="bi bi-book me-2"></i>Docs</a>
                         <a href="https://github.com/ArduPilot/CustomBuild/issues/new" class="btn btn-outline-light me-1"><i