Adjust example for SFML 3

Author: peytonk132

README.md

@@ -114,9 +114,9 @@ int main() {
     sf::Clock deltaClock;
     while (window.isOpen()) {
         while (const auto event = window.pollEvent()) {
-            ImGui::SFML::ProcessEvent(window, event);
+            ImGui::SFML::ProcessEvent(window, *event);
 
-            if (event.type == sf::Event::Closed) {
+            if (event->is<sf::Event::Closed>()) {
                 window.close();
             }
         }