Implement basic UI for rate code

Description

This MR partially implements https://gitlab.com/gitlab-org/gitlab/-/issues/415773 providing a basic user flow UI for model rating.

What is NOT implemented and will be added later

• Storing of rated prompts
• Generation of the session id
• Integration with the voting endpoint

Video recording

https://www.loom.com/share/7ff3fb202c774884ad96e8a8cbfc17ed

how to reproduce

1. run yarn and yarn dev in eval-code-viewer folder
2. navigate to localhost:3000/rate-prompts page and interact with the website