[Header Area] Add links and actions under settings icon

[RabebOthmani]

As a user,
When I click on the settings icon
I see a drop-down list of actions

Acceptance Criteria

• Responsive design
• Accessibility
• Telemetry: measure clicks on each of the links except for change theme
• Actions and links:
  • change theme (functionality is same as the current experience)
  • Report an issue (functionality is same as the current experience)
  • Documentation: click opens up https://docs.microsoft.com/en-us/graph/api/overview?view=graph-rest-1.0 in a new tab
  • GitHub: click opens up https://github.com/microsoftgraph/microsoft-graph-explorer-v4 in a new tab

Design
Please refer to figma file for design requirements