Add a boundary error page

[AntoLC]

Feature Request

We still have the default Next.js page when the app crashes.
"Application error: a client-side exception has occurred while loading docs.numerique.gouv.fr (see the browser console for more information)."

• Integrate a error boundary page with a correct design and message.
• Propose a link to come back to the previous page
• Send error to sentry

We could keep something simple in this spirit, with a more appropriate image: