Code editor: Provide PF styles for code syntax

[andrew-ronaldson]

Goal

PatternFly Code editor ships with the default colour scheme from the Monaco editor. In order to work with our theming capabilities we would like to define a set of colour tokens that can be used in the component.

Planning

Take syntax examples from JS, CSS, HTML and YAML to better understand the parameters and combinations that we need to support.
Include recommendations for high contrast theme if needed.