infoString property
The 'info string'.
This includes any text (trimming whitespace) following the opening backticks (for a fenced code block). For example, in a fenced code block starting with "```dart", the info string is "dart".
If the code block is an indented code block, or a fenced code block with
no text following the opening backticks, the info string is null.
See CommonMark specification at spec.commonmark.org/0.30/#fenced-code-blocks.
Implementation
final String? infoString;