- Implemented runtime API for registering custom highlighters.
- Added optional Tree-sitter integration for advanced syntax parsing (disabled by default).
- Updated buffer initialization and copying to support dynamic highlighter configuration.
- Introduced `NullHighlighter` as a fallback for unsupported filetypes.
- Enhanced CMake configuration with `KTE_ENABLE_TREESITTER` option.
- Introduced `HighlighterRegistry` with support for multiple language highlighters (e.g., JSON, Markdown, Python).
- Added `JsonHighlighter` implementation for basic JSON syntax highlighting.