Add a `contributors` page

## Requirements :

- [ ] A new `contributors.html` page ;
- [ ] The new page should have a `` with `id` attribute with `contributors` value ;
- [ ] This page should have the same styles as the homepage (`index.html`) ;

## Notes :

No need to list any contributor by hand in this feature. This will be made with another one.

Start by reading index.html to identify the homepage structure and styles. Create contributors.html with a table whose id is contributors, matching the homepage styling; do not add contributor entries by hand. Done means the new page exists and satisfies all listed requirements.

Written by the indexing model from the issue text.