Header: Design system website contextual example updates

[Spark450]

Acceptance Criteria:

• Fix current header with navigation example so that hover/focus treatment on "tickets" nav item spans full height
• Add jump links below the properties accordion:
  • Header with navigation
  • Sign in using the site header
  • Access user settings in the site header
• Add the following examples and code snippets below the "Header with navigation" example (Figma design)
  • Sign in using the site header
  • Access user settings in the site header