Enhance documentation

[louismaximepiton]

Prerequisites

• I have searched for duplicate or closed feature requests
• I have read the contributing guidelines

Proposal

Proposals:

• Use a <main> for a11y and use .container-xxl instead of .container everywhere if possible.
• Set up the use_cases page with a side menu and links to anchor in the page to ease the UX. We'll need to figure out how to manage such an amount of charts, maybe using some <iframe loading="lazy"> could help ? More info here: Can't click on a link placed in a tooltip #248 (comment).

Motivation and context

Better the documentation.