pub fn prefix_string(&self) -> String {
        match self {
            CommentVariant::TripleSlash => "///".into(),
            CommentVariant::DoubleSlashEM => "//!".into(),
            CommentVariant::MacroDocEqMacro => "".into(),
            CommentVariant::MacroDocEqStr(d, p) => {
                let raw = match p {
                    // TODO: make configureable if each line will start with #[doc ="
                    // TODO: but not here!
                    0 => "\"".to_owned(),
                    x => format!("r{}\"", "#".repeat(x.saturating_sub(1))),
                };
                format!(r#"{d}{raw}"#)
            }
            CommentVariant::CommonMark => "".to_string(),
            CommentVariant::DoubleSlash => "//".to_string(),
            CommentVariant::SlashStar => "/*".to_string(),
            CommentVariant::SlashAsterisk => "/*".to_string(),
            CommentVariant::SlashAsteriskEM => "/*!".to_string(),
            CommentVariant::SlashAsteriskAsterisk => "/**".to_string(),
            CommentVariant::TomlEntry => "".to_owned(),
            unhandled => {
                unreachable!("String representation for comment variant {unhandled:?} exists. qed")
            }
        }
    }
Return the prefix string.

Does not include whitespaces for `///` and `//!` variants!
doc-chunks/src/literal.rs