Accordion Menu: Submenu Toggle

• Any link with a submenu should contain a .submenu-toggle button.
• This button should toggle the submenu.
• The parent link (if it has a link) should work as a link.

• Item 1 (external)
  • Item 1A (external)
  • Item 1B
• Item 2
  • Item 2A
  • Item 2B
    • Item 2BA (external)
    • Item 2BB