Mermaid support

[KtorZ]

It'd be cool if the markdown renderer on the website had support for Mermaid.js so that diagrams such as those from CIP-0045 render just fine ☺️

[fill-the-fill]

@KtorZ I'm seeing that Mermaid has an issue with our current NextJs version and a lot of people recommending downgrading NextJs. What do you think about that?

[KtorZ]

Unless there are crucial points we need from the current version then, downgrading sounds reasonable.

[rphair]

@fill-the-fill @KtorZ Mermaid is coming into more CIPs (e.g. cardano-foundation/CIPs@bebfb13) and is now in the CIP process documentation itself (here). Will we have Mermaid rendering on cips.cardano.org soon, or should I advise authors to only expect it on GitHub? (cc @Ryun1 @Crypto2099)

Merged with Mermaid so far (currently with diagrams unrendered):

• https://cips.cardano.org/cip/CIP-0045