I added a small playground to the homepage, please feel free to try it and let me know what you think!
It's not perfect, it's definitely not "correct" in that I'm using Regex internally instead of a proper AST parser, but for my usecase and the majority of Markdown out there, this works perfectly fine (cue the StackOverflow post [1]). It's also conservative for this reason; no HTML by default, parsing wrong content produces escaped HTML entities instead of XSS.