Port the miscellaneous resources to Next.js

[bfabio]

Port these resources to Next.js:

• [ ] 403.html, 404.html and 500.html error pages
• [ ] favicon.ico
• [ ] the static assets (images, attachments and icons)
• [ ] security.txt

Gotchas

The in /images/posts, contains the "attachments" to the news pages and are mostly non-images/PDFs, despite the name of the directory.