A styled markdown initializer for AttributedString

AttributedString.swift

extension AttributedString {
    init(styledMarkdown markdownString: String) throws {
        let newLine = AttributedString("\n")
        let markdownString = markdownString
            .replacingOccurrences(of: "\n\n", with: "\u{2029}\u{2029}\n\n")
        
        var output = try AttributedString(
            markdown: markdownString,
            options: .init(
                allowsExtendedAttributes: true,
                interpretedSyntax: .full,
                failurePolicy: .returnPartiallyParsedIfPossible
            ),
            baseURL: nil
        )
        
        while let range = output.range(of: "\u{2029}\u{2029}") {
            output[range] = newLine[newLine.startIndex..<newLine.endIndex]
        }

        for (intentBlock, intentRange) in output.runs[AttributeScopes.FoundationAttributes.PresentationIntentAttribute.self].reversed() {
            guard let intentBlock = intentBlock else { continue }
            for intent in intentBlock.components {
                switch intent.kind {
                case .header(level: let level):
                    switch level {
                    case 1:
                        output[intentRange].font = .system(.title).bold()
                    case 2:
                        output[intentRange].font = .system(.title2).bold()
                    case 3:
                        output[intentRange].font = .system(.title3).bold()
                    default:
                        break
                    }
                default:
                    break
                }
            }
            
            if intentRange.lowerBound != output.startIndex {
                output.characters.insert(contentsOf: "\n", at: intentRange.lowerBound)
            }
        }

        self = output
    }
}