[windows] Support drawing a frame for frameless to support hiding the titlebar

v2/pkg/options/windows/windows.go

@@ -5,4 +5,7 @@ type Options struct {
 	WebviewIsTransparent bool
 	WindowIsTranslucent  bool
 	DisableWindowIcon    bool
+
+	// Draw a border around the window, even if the window is frameless
+	EnableFramelessBorder bool
 }