Create a route / query to get active semester

[kerfootj]

User Story

As a developer, I want to be able to retrieve which semesters have open registration

Description

Create a route /semesters that returns the current active semesters.

Additional Details

May want to use a query param like ?active=true so historical data can also be requested in the future

Acceptance Criteria

• [ ] Making a Get request to /semesters returns some semester data

[kerfootj]

You don't need the query param ?active for now. We'll add it later if we need to.