Como adicionar marcação personalizada ao MarkupVisitor no Swift-Markdown?

Estou usando a biblioteca swift-markdown no meu aplicativo.

Estou tentando descobrir como adicionar meu próprio costume Markupao MarkupVisitor?

Consegui usar uma solução alternativa visitInlineAttributesque se aplica a ^[]().

Existe uma maneira de adicionar minha própria marcação personalizada?

Por exemplo, se eu quisesse minha própria marcação inline onde o texto dentro @[text]teria cor cinza? Semelhante a como **bold** deixa as coisas em negrito.

Alguém fez essa pergunta na biblioteca, mas não entendi como implementar a única resposta lá.

https://github.com/swiftlang/swift-markdown/issues/122

Aqui está um exemplo que eu tenho:

import UIKit
import Markdown
import SnapKit

class ViewController: UIViewController, UITextViewDelegate {
    
    let label = UITextView()

    override func viewDidLoad() {
        super.viewDidLoad()
        
        label.isEditable = false
        label.delegate = self
        label.linkTextAttributes = [:]
        view.addSubview(label)
        label.snp.makeConstraints { make in
            make.edges.equalTo(view.safeAreaLayoutGuide).inset(10)
        }
        
        var md = MarkdownParser()
        let attr = md.attributedString(from: "Hello World! Here's some text which is **bold** and here's some which is *italics*. Here's some ^[[metadata containing link](https://old.reddit.com/r/SaaS/comments/1fgv248/fuck_founder_mode_work_in_fuck_off_mode/)]() which is gray and not underlined. And here's some normal [link](https://hckrnews.com) which is underlined and red. You are welcome!")
        print("ATTR:\n\n\(attr)")
        label.attributedText = attr
        
    }
    
    func textView(_ textView: UITextView, shouldInteractWith URL: URL, in characterRange: NSRange, interaction: UITextItemInteraction) -> Bool {
        print("shouldInteractWith: \(URL)")
        return true
    }

}

struct MarkdownParser: MarkupVisitor {

    typealias Result = NSMutableAttributedString
    
    mutating func attributedString(from : String) -> NSMutableAttributedString {
        let document = Document(parsing: from)
        print(document.debugDescription())
        return NSMutableAttributedString(attributedString: visit(document))
    }
    
    mutating func visit(_ markup: Markup) -> NSAttributedString {
        return markup.accept(&self)
    }
    
    mutating func defaultVisit(_ markup: any Markdown.Markup) -> NSMutableAttributedString {
        let result = NSMutableAttributedString()

        for child in markup.children {
            result.append(visit(child))
        }

        return result
    }
    
    mutating func visitText(_ text: Text) -> NSMutableAttributedString {
        return NSMutableAttributedString(string: text.plainText, attributes: [.font:UIFont.systemFont(ofSize: 18, weight: .regular),.foregroundColor:UIColor.label])
    }
    
    mutating func visitEmphasis(_ emphasis: Emphasis) -> NSMutableAttributedString {
        return doVisit(emphasis)
    }
    
    mutating func visitStrong(_ strong: Strong) -> NSMutableAttributedString {
        return doVisit(strong)
    }
    
    mutating func visitInlineAttributes(_ attributes: InlineAttributes) -> NSMutableAttributedString {
        return doVisit(attributes)
    }
    
    mutating func visitLink(_ link: Link) -> NSMutableAttributedString {
        return doVisit(link)
    }
    
    mutating func doVisit(_ markup: any Markup) -> NSMutableAttributedString {
        let result = NSMutableAttributedString()
        
        for child in markup.children {
            result.append(visit(child))
        }
        
        switch markup {
        case is Strong:
            fallthrough
        case is Emphasis:
            result.enumerateAttribute(.font, in: result.fullRange, options: []) { value, range, stop in
                if let newFont = (value as? UIFont)?.addTrait(trait: markup is Strong ? .traitBold : .traitItalic) {
                    result.addAttribute(.font, value: newFont, range: range)
                }
            }
        case is InlineAttributes:
            result.removeAttributes([.underlineStyle,.underlineColor])
            result.addAttribute(.foregroundColor, value: UIColor.tertiaryLabel)
        case is Link:
            if let destination = (markup as? Link)?.destination, let url = URL(string: destination) {
                let color = UIColor.systemRed
                result.addAttributes([.underlineStyle : NSUnderlineStyle.single.rawValue, .underlineColor : color,.foregroundColor : color, .link : url])
            }
        default:
            break
        }
        
        return result
    }
}

extension NSAttributedString {
    var fullRange : NSRange {
        NSRange(location: 0, length: length)
    }
}

extension NSMutableAttributedString {
    func addAttribute(_ name: NSAttributedString.Key, value: Any) {
        addAttribute(name, value: value, range: fullRange)
    }

    func addAttributes(_ attrs: [NSAttributedString.Key : Any]) {
        addAttributes(attrs, range: fullRange)
    }
    
    func removeAttribute(_ name: NSAttributedString.Key) {
        removeAttribute(name, range: fullRange)
    }
    
    func removeAttributes(_ names: [NSAttributedString.Key]) {
        for attribute in names {
            removeAttribute(attribute)
        }
    }
}

extension UIFont {
    func addTrait(trait : UIFontDescriptor.SymbolicTraits) -> UIFont {
        var traits = fontDescriptor.symbolicTraits
        if traits.contains(trait) {
            return self
        } else {
            traits.insert([trait])
            return UIFont(descriptor: fontDescriptor.withSymbolicTraits(traits)!, size: pointSize)
        }
    }
}

Isso mostra o seguinte: