PHP 8.1 compatibility

Problem/Motivation

Deprecated function: Return type of Elphin\IcoFileLoader\Icon::offsetExists($offset) should either be compatible with ArrayAccess::offsetExists(mixed $offset): bool, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in include() (line 8 of /var/www/html/vendor/lordelph/icofileloader/src/Icon.php)

#0 /var/www/html/core/includes/bootstrap.inc(347): _drupal_error_handler_real()
#1 /var/www/html/vendor/lordelph/icofileloader/src/Icon.php(8): _drupal_error_handler()
#2 /var/www/html/vendor/composer/ClassLoader.php(571): include('...')
#3 /var/www/html/vendor/composer/ClassLoader.php(428): Composer\Autoload\includeFile()
#4 /var/www/html/vendor/lordelph/icofileloader/src/IcoParser.php(69): Composer\Autoload\ClassLoader->loadClass()
#5 /var/www/html/vendor/lordelph/icofileloader/src/IcoParser.php(55): Elphin\IcoFileLoader\IcoParser->parseICO()
#6 /var/www/html/vendor/lordelph/icofileloader/src/IcoFileService.php(126): Elphin\IcoFileLoader\IcoParser->parse()
#7 /var/www/html/vendor/lordelph/icofileloader/src/IcoFileService.php(111): Elphin\IcoFileLoader\IcoFileService->fromFile()
#8 /var/www/html/modules/contrib/standwithukraine/src/Service/StandWithUkraineFavicon.php(87): Elphin\IcoFileLoader\IcoFileService->from()
#9 /var/www/html/modules/contrib/standwithukraine/src/Form/StandWithUkraineForm.php(165): Drupal\standwithukraine\Service\StandWithUkraineFavicon->build()
#10 [internal function]: Drupal\standwithukraine\Form\StandWithUkraineForm->buildForm()
#11 /var/www/html/core/lib/Drupal/Core/Form/FormBuilder.php(531): call_user_func_array()
#12 /var/www/html/core/lib/Drupal/Core/Form/FormBuilder.php(278): Drupal\Core\Form\FormBuilder->retrieveForm()
#13 /var/www/html/core/lib/Drupal/Core/Controller/FormController.php(73): Drupal\Core\Form\FormBuilder->buildForm()
#14 [internal function]: Drupal\Core\Controller\FormController->getContentResult()
#15 /var/www/html/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(123): call_user_func_array()
#16 /var/www/html/core/lib/Drupal/Core/Render/Renderer.php(564): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}()
#17 /var/www/html/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(124): Drupal\Core\Render\Renderer->executeInRenderContext()
#18 /var/www/html/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(97): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext()
#19 /var/www/html/vendor/symfony/http-kernel/HttpKernel.php(158): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}()
#20 /var/www/html/vendor/symfony/http-kernel/HttpKernel.php(80): Symfony\Component\HttpKernel\HttpKernel->handleRaw()
#21 /var/www/html/core/lib/Drupal/Core/StackMiddleware/Session.php(58): Symfony\Component\HttpKernel\HttpKernel->handle()
#22 /var/www/html/core/lib/Drupal/Core/StackMiddleware/KernelPreHandle.php(48): Drupal\Core\StackMiddleware\Session->handle()
#23 /var/www/html/core/modules/ban/src/BanMiddleware.php(50): Drupal\Core\StackMiddleware\KernelPreHandle->handle()
#24 /var/www/html/core/lib/Drupal/Core/StackMiddleware/ReverseProxyMiddleware.php(48): Drupal\ban\BanMiddleware->handle()
#25 /var/www/html/core/lib/Drupal/Core/StackMiddleware/NegotiationMiddleware.php(51): Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle()
#26 /var/www/html/vendor/stack/builder/src/Stack/StackedHttpKernel.php(23): Drupal\Core\StackMiddleware\NegotiationMiddleware->handle()
#27 /var/www/html/core/lib/Drupal/Core/DrupalKernel.php(709): Stack\StackedHttpKernel->handle()
#28 /var/www/html/index.php(19): Drupal\Core\DrupalKernel->handle()
#29 {main}

Proposed resolution

Declare return type for some functions of the icon file of the Elphin IcoFileLoader library in format PHP 8.1.