Update MainMenu part of README to reflect admin updates
Update MainMenu part of README to reflect admin updates

ababic/wagtailmenus,frague59/wagtailmenus,rkhleics/wagtailmenus,ababic/wagtailmenus,rkhleics/wagtailmenus,frague59/wagtailmenus,ababic/wagtailmenus,frague59/wagtailmenus,rkhleics/wagtailmenus