Moved the menu to a new structure.

internal/gui/window/main.go

@@ -9,6 +9,7 @@ import (
 
 type WindowContract interface {
 	SetContent(content fyne.CanvasObject)
+	SetMainMenu(menu *fyne.MainMenu)
 	Show()
 	InitLayout()
 	NewFileOpen(callback func(fyne.URIReadCloser, error), location fyne.ListableURI) *dialog.FileDialog
@@ -42,6 +43,12 @@ func NewMainWindow(
 	}
 }
 
+func (w *mainWindow) SetMainMenu(menu *fyne.MainMenu) {
+	fyne.Do(func() {
+		w.fyneWindow.SetMainMenu(menu)
+	})
+}
+
 func (w *mainWindow) InitLayout() {
 	fyne.Do(func() {
 		w.layout = NewLayout(w.progressBarService, w.itemsToConvert, w.queueLayout)