allow showing, hiding, and scrolling the extras panel

pkg/gui/extras_panel.go

@@ -0,0 +1,15 @@
+package gui
+
+func (gui *Gui) handleCreateExtrasMenuPanel() error {
+	menuItems := []*menuItem{
+		{
+			displayString: "Toggle show/hide command log",
+			onPress: func() error {
+				gui.ShowExtrasWindow = !gui.ShowExtrasWindow
+				return nil
+			},
+		},
+	}
+
+	return gui.createMenu(gui.Tr.DiffingMenuTitle, menuItems, createMenuOptions{showCancel: true})
+}