devtools: persist fsr configs (#2852)

Saves FSR config to imgui.ini so it won't reset every startup

src/imgui/renderer/imgui_core.cpp

@@ -112,6 +112,8 @@ void Initialize(const ::Vulkan::Instance& instance, const Frontend::WindowSDL& w
     if (const auto dpi = SDL_GetWindowDisplayScale(window.GetSDLWindow()); dpi > 0.0f) {
         GetIO().FontGlobalScale = dpi;
     }
+
+    std::at_quick_exit([] { SaveIniSettingsToDisk(GetIO().IniFilename); });
 }
 
 void OnResize() {