Header: Test skiplinks

[gfellerph]

Test the skiplink functionality of the internet header with cypress.

• [X] Skiplinks="true": Skiplinks should be rendered
• [X] Skiplinks="false": Skiplinks should not be rendered
• [ ] Skip to search should open the search flyout and focus the search input field
• [ ] Skip to main content should be hidden if there is no
  element on the page
• [ ] Skip to main content should set the focus to the
  element and scroll it into view
• [ ] Skip to main navigation should focus the first main navigation link
• [ ] Skip to login should redirect to the login