feat: added custom callout component

[brokewhale]

Description

Adds support for custom callout messages in the SpecialCallout component. This feature allows you to add a custom callout to a page, notifying users that it is currently undergoing maintenance.

Additional context

import { SpecialCallout } from '@/components/SpecialCallout';

<SpecialCallout /> // with default message
<SpecialCallout context="this tutorial is outdated" /> // with message

This is an image showing that the callout sticks to the top when the page is scrolled

The color scheme is open for suggestions, and I'll update this PR accordingly.

Example link: http://localhost:3000/builders/app-developers/tutorials/cross-dom-bridge-erc20