feat: add custom C++ syntax highlighting support

[julioest]

Implements a custom lightweight C++ syntax highlighter to replace highlight.js for consistent code styling.

Changes

• Created cpp-highlight.js with comprehensive C++ language support
• Added cpp-highlight.css for syntax highlighting styles
• Integrated highlighter into the Antora UI bundle

Syntax Highlighting

• Keywords: Blue, bold (e.g., const, if, class, template)
• Strings: Dark red (#a31515) - handles raw strings, prefixes (L, u8, U)
• Preprocessor: Purple (#6f008a) - #include, #define, etc.
• Comments: Green (#008000), italic (C++ and C-style)
• Identifiers: Default black (function names, variables, etc.)

Features

• Supports C++20 features (concepts, coroutines, modules)
• Handles raw string literals with delimiters
• Processes multi-line preprocessor directives
• Correctly identifies preprocessor at line start only

Fixes issue with inconsistent C++ syntax highlighting colors.

Related to boostorg/website-v2#2033

[cppalliance-bot]

An automated preview of the documentation is available at https://556.site-docs.prtest2.cppalliance.org/index.html

If more commits are pushed to the pull request, the docs will rebuild at the same URL.

2025-12-12 21:14:33 UTC