Update homepage design to allow clicking into either the 2023 or 2024 elections

Since both the 2023 election and 2024 elections are currently in the future, we want to allow viewing the data for either. Add two buttons? How should the homepage look?

Before:
<img width="939" alt="image" src="https://github.com/caciviclab/disclosure-backend-static/assets/129120/ca7e823d-6e07-48b6-89a9-60271c86a69e">
