Accessibility - Hamburger menu is missing focus indicator when tabbing through fields

[maur1]

Current Behavior

Hamburger menu is missing focus indicator when tabbing through fields

Proposed Behavior

Add CSS to ensure the menu button has a visible focus state

Checklist

• I have read and understand the contributing guidelines
• I have checked the existing issues for whether this enhancement was already requested

[Killian-Aidalinfo]

Hello, I made the change in this PR : #1211