qt: set default "window icon" (only visible on Windows)

electrum/gui/qt/__init__.py

@@ -97,6 +97,7 @@ class ElectrumGui(PrintError):
         self.efilter = OpenFileEventFilter(self.windows)
         self.app = QElectrumApplication(sys.argv)
         self.app.installEventFilter(self.efilter)
+        self.app.setWindowIcon(read_QIcon("electrum.png"))
         # timer
         self.timer = QTimer(self.app)
         self.timer.setSingleShot(False)