macOS: use "PySolFC Help" menuitem provided by tk

The details are explained in this tutorial
https://tkdocs.com/tutorial/menus.html

For this to work, init() must destroy the tkinter.Tk instance it creates
so that was uncommented.

pysollib/init.py

@@ -117,7 +117,7 @@ def init():
             else:
                 pysollib.settings.USE_TILE = True
         # "can't invoke event <<ThemeChanged>>: application has been destroyed"
-        # root.destroy()
+        root.destroy()
         tkinter._default_root = None
 
     # check FreeCell-Solver

pysollib/ui/tktile/menubar.py

@@ -646,10 +646,16 @@ class PysolMenubarTkCommon:
         if self.progress:
             self.progress.update(step=1)
 
+        # macOS: tk creates the menu item "Help->PySolFC Help", therefore
+        # we will not create a duplicate "Help->Contents" item.
+        # The tk-provided menu item expects this callback.
+        self.top.createcommand('tk::mac::ShowHelp', self.mHelp)
+
         menu = MfxMenu(self.menubar, label=n_("&Help"))
-        menu.add_command(
-            label=n_("&Contents"),
-            command=self.mHelp, accelerator=m+"F1")
+        if WIN_SYSTEM != "aqua":
+            menu.add_command(
+                label=n_("&Contents"),
+                command=self.mHelp, accelerator=m+"F1")
         menu.add_command(
             label=n_("&How to play"),
             command=self.mHelpHowToPlay)

pysollib/ui/tktile/tkutil.py

@@ -112,6 +112,7 @@ def make_help_toplevel(app, title=None):
     from pysollib.winsystems import init_root_window
     window = tkinter.Toplevel(class_=TITLE)
     init_root_window(window, app)
+    window.tkraise()
     return window