feat: update dependencies and enhance article rendering

- Added new dependencies for rehype and remark processing to improve HTML rendering of articles.
- Updated the hashing algorithm for article headings from SHA-256 to SHA-512 for better security.
- Modified CSS styles for article content to improve visual presentation.
- Removed unused remark-html dependency and added highlight.js for syntax highlighting.
- Created a new highlight.css file for custom styles related to code highlighting.

Author: The-Infinitys