Driver Availability: Added Navbar

[Rytuose]

We added a navbar for driver availability so admins and drivers can access the index, edit, and create pages for driverAvailability. The current pages are placeholders.

Acceptance Criteria: Driver Perspective

• [x] Any driver (ROLE_DRIVER) should be able to see a menu option Availability under Shifts on the navbar.

Acceptance Criteria: Admin Perspective

• [x] Under the admin option of the navbar there is an option Driver Availability where they can see all drivers' availability.

Closes #52

[shamitagurusu]

LGTM 👍

[shamitagurusu]

LGTM 👍 👍