[refactor] add namespace 'crossdesk' to codebase

src/gui/windows/main_settings_window.cpp

@@ -3,6 +3,8 @@
 #include "rd_log.h"
 #include "render.h"
 
+namespace crossdesk {
+
 int Render::SettingWindow() {
   if (show_settings_window_) {
     if (settings_window_pos_reset_) {
@@ -390,4 +392,5 @@ int Render::SettingWindow() {
   }
 
   return 0;
-}
+}
+}  // namespace crossdesk