init(String) Wraps up a String with Markdown inside.
struct MarkdownStringlet markdown = MarkdownString("# Hello")
let html = markdown.toHTML()
print(html) // "<h1>Hello</h1>"
print(markdown.description) // "# Hello"
init(String) Swift.Copyable Swift.CustomStringConvertible Swift.LosslessStringConvertible Swift.Sendable