Namespace Editor Highlighting

The core types are IHighlightingDefinition (describes a language's highlighting rules), DocumentHighlighter (applies rules to a TextDocument producing HighlightedLines), and HighlightingManager (registry of built-in and user-loaded definitions, with lookup by name or file extension).

Built-in definitions include C#, C++, Java, JavaScript, Python, PowerShell, TSQL, VB, JSON, HTML, XML, CSS, and Markdown. Highlight colors compose with the active Terminal.Gui color scheme.