message: FilamentApp: use PrtScn key to capture debug frame
diff: #include <filament/Skybox.h>
  #include <filament/View.h>
  +#ifndef NDEBUG
  +#include <filament/DebugRegistry.h>
  +#endif
  +
  #include <filagui/ImGuiHelper.h>
  #include <filamentapp/Cube.h>
  @@ -272,6 +276,14 @@ void FilamentApp::run(const Config& config, SetupCallback setupCallback,
  if (event.key.keysym.scancode == SDL_SCANCODE_ESCAPE) {
  mClosed = true;
  }
  +#ifndef NDEBUG
  + if (event.key.keysym.scancode == SDL_SCANCODE_PRINTSCREEN) {
  + DebugRegistry& debug = mEngine->getDebugRegistry();
  + bool* captureFrame =
  + debug.getPropertyAddress<bool>("d.renderer.doFrameCapture");
  + *captureFrame = true;
  + }
  +#endif
  window->keyDown(event.key.keysym.scancode);
  break;
  case SDL_KEYUP:
  