Add styles and improve a11y

[kirahsapong]

• adds styles and favicon
• adds a11y improvements
• conditionally displays accordion when list contains items

[kirahsapong]

@nitro-neal would it be valuable to hyperlink the name of the test to the relevant test vector json do you think?

[nitro-neal]

Yo this looks great! thank you 🥇

I think they dont need to link, maybe one link at the top or bottom somewhere that brings them to the test-vectors folder