This is just a thin-but-pleasant Swifty wrapper over my feature-free, SPM-enabling fork of Fletcher Penny's excellent MultiMarkdown-6.
The simplest use is to call a single static method.
static func convert(_ source: String, to format: Format = .html, extensions: Extensions = []) throws -> StringMultiMarkdownSwift also supports extracting metadata from a source:
let doc = try MultiMarkdown(source: src)
let meta = doc.getMetadata()
let value: String? = meta["author"]