add structed text code highlighting

[rruiter87]

https://github.com/benhar-dev/mobject-core/tree/main/docs/docsify

[Roald87]

not so easy I think. Either

• need to build a custom structured text lexer with rogue https://github.com/rouge-ruby/rouge/blob/master/lib/rouge/lexers/json.rb
• or somehow get prism to work https://prismjs.com/index.html in the github pages pipeline