fn heading_level(line: &str) -> Option<usize>Expand description
Determine the Markdown heading level for a single line.
Returns Some(1), Some(2), or Some(3) when the line starts with "# ", "## ", or "### "
respectively, and None for any other input.
§Examples
ⓘ
assert_eq!(heading_level("# Title"), Some(1));
assert_eq!(heading_level("## Subtitle"), Some(2));
assert_eq!(heading_level("### Section"), Some(3));
assert_eq!(heading_level("#### Too deep"), None);
assert_eq!(heading_level("Not a heading"), None);