Update Header

There are a couple changes that need to be made to the header,
https://designsystem.digital.gov/components/header/

To Do:

• create Interface to define navigation links export Interface Navigation
• update markup

  <!-- pseudocode -->
  <logo></logo>
  <contributor-logo></contributor-logo>
  <navigation>
    <button></button>
    <secondary-nav></secondary-nav> // application navigation
    <primary-nav></primary-nav> // site navigation
    <search></search>
  </navigation>

  • Add menu button
  • Add primary navigation
  • Add placeholder for secondary navigation to header (to be added by #29 (closed))
    • Do not show secondary navigation on desktop
    • Show secondary navigation on mobile
  • Add cooperator logo
    • Create interface export Interface Cooperator
    • Add markup to header for a link wrapped image
• Update example on example project