Additional languages code Markdown

[Luvideria]

referring issue #562
#562 (comment)

are there others we should add by default? With the caveat that we don't want to include all available languages, that would be too big. So we should also document the process to make & use your own hljs build (https://highlightjs.org/download/#cdns) - also requires that we implement something like plotly/dash#655

We can discuss here which languages to import in the default package and perhaps an easy way to import additional languages (as pointed in plotly/dash#655).
Documentation is needed for these topics.

[wbrgss]

These are the languages that are supported now:

• Bash
• CSS
• HTML, XML
• HTTP
• JavaScript
• JSON
• Markdown
• Python
• R
• "Shell Session" (shell ...)
• SQL

Some additions that might be useful (from my own unscientific observations of what's popular):

• C/C++
• Excel
• Go
• Haskell
• Java
• Julia
• Lua
• Matlab
• OCaml
• ReasonML
• Ruby
• Rust
• SAS
• Scala
• SCSS
• TeX
• TypeScript (can't remember if this made it in)