Syntax highlighting Issues

[dimodi]

Describe the bug

• It doesn't matter what language is set for a code snippet. The syntax lighting is always the same. For some languages, the code looks relatively OK, but not always. For example, CSS snippets are almost unstyled.
• There is no internal documentation about the supported languages and what is the correct syntax to define a language for a code block (here in README or in the Docs Style Guide). Do we use 3 backticks or 4? Do we type the language name in lowercase or in uppercase?
• There is limited language support. We are missing HTML, CSS and TypeScript.

To Reproduce
Steps to reproduce the behavior:

1. Use a page with HTML, CSS, JS, C# snippets.
2. Add, remove or change the language to see there is no difference in the syntax highlighting.

Expected behavior

• Language definition should matter. Syntax highlighting should be correct for the language specifics.
• We should have an internal documentation how to use syntax highlighting and how to use code tabs.
• Syntax highlighting should support HTML, CSS, JS, C#, TypeScript