Implement header navigation component

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• Implement non-interactive menu for mobile and large screens
• Implement a minimal interactive menu for large screens
• Implement a minimal, interactive menu for mobile screens
• Update to match current large screen and mobile screen Figma designs (could be a few hours or two days, depending on complexity of CSS)
• Change large screen menu to use hidden instead of opacity to fix subtle issue with hidden menu capturing mouse events
• Change large screen menu to use z-order to ensure dropdown menus always appear above other content

[ghost]

• Implement a simple, interactive menu for large screens

Done in #160

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• Implement non-interactive menu for mobile and large screens

This was done in #86

[ghost]

Implement a simple, interactive menu for mobile screens

This step will implement the logic to show and hide the mobile hamburger menu. #172 will implement the content that resides inside of the dropdown menu, once this logic is in place.

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Tailwind didn't indicate this clearly, but I needed to make use of both z-order and hidden classes to cause proper showing and hiding.

[ghost]

• Implement a minimal, interactive menu for mobile screens

Completed in #209

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• Change large screen menu to use hidden instead of opacity to fix subtle issue with hidden menu capturing mouse events

Done within this PR

[ghost]

Attempt refactoring implementation to make use of headless-ui library (timebox this, create a follow-up issue if it turns out to be complex)

This appears to be partially or fully done in PR #385.