message: Use constructor init list for control text in DifficultySelect
diff: #include "SDL2/SDL_video.h"
  -DifficultySelect::DifficultySelect() : Window()
  +DifficultySelect::DifficultySelect() :
  + rdbBeginner{constants::DIFFICULTY_BEGINNER},
  + rdbEasy{constants::DIFFICULTY_EASY},
  + rdbMedium{constants::DIFFICULTY_MEDIUM},
  + rdbHard{constants::DIFFICULTY_HARD},
  + btnOk{"Ok"}
  {
  text(constants::DIFFICULTY_TITLE);
  init();
  @@ -51,7 +56,6 @@ void DifficultySelect::init()
  const auto bottom_edge = top_edge + height() - border_top_height - border_bottom_height * 2.0f;
  const auto width = right_edge - left_edge;
  - btnOk.text("Ok");
  btnOk.size(100, 25);
  btnOk.click().connect(this, &DifficultySelect::btnOkClicked);
  @@ -64,11 +68,6 @@ void DifficultySelect::init()
  default: rdbBeginner.checked(true); break;
  }
  - rdbBeginner.text(constants::DIFFICULTY_BEGINNER);
  - rdbEasy.text(constants::DIFFICULTY_EASY);
  - rdbMedium.text(constants::DIFFICULTY_MEDIUM);
  - rdbHard.text(constants::DIFFICULTY_HARD);
  -
  float longest_width = 0.0f;
  if (longest_width < rdbBeginner.width())
  {
  