start using highlight.js to highlight structured data

[erwindon]

Is your feature request related to a problem? Please describe.
Currently, a simple CSS is used to present structured values, e.g. grain-values.
This is difficult to maintain as structure (lines/indentation/spacing/wrapping) must remain optimal.

Describe the solution you'd like
Introduce highlight.js and use that for both coloring and layout.

Additional context

• must check whether license is matching the other licenses;
• must check whether all data types (json/yaml/nested) are supported;
  • json --> ok
  • yaml --> ok
  • nested --> need to find compatible rules
• must check whether the colors still look good;
• optionally add an option to switch it off from master-config.

[erwindon]

replaced by #624