[refactor] add namespace 'crossdesk' to codebase

src/gui/tray/win_tray.cpp

@@ -4,6 +4,8 @@
 
 #include "localization.h"
 
+namespace crossdesk {
+
 // callback for the message-only window that handles tray icon messages
 static LRESULT CALLBACK MsgWndProc(HWND hwnd, UINT msg, WPARAM wParam,
                                    LPARAM lParam) {
@@ -109,4 +111,5 @@ bool WinTray::HandleTrayMessage(MSG* msg) {
     }
   }
   return true;
-}
+}
+}  // namespace crossdesk