feat: add fieldset for the checkboxes input

[Sboonny]

• [x] I have read Chapter's contributing guidelines.
• [x] My pull request has a descriptive title (not a vague title like Update README.md).
• [x] My pull request targets the main branch of Chapter.

adding fieldset and legend to add context for screen readers

[ghost]

👇 Click on the image for a new way to code review

#### [](https://app.codesee.io/r/reviews?pr=2465&src=https%3A%2F%2Fgithub.com%2FfreeCodeCamp%2Fchapter) #### Legend

[Sboonny]

Added little margintop for clearance for visual users