You might want to consider changing the name. It's not great practice to use the name of someone else's open source thing to name yours. It's fine in the tagline.
there is a PHP and python "Markdownify" , both are HTML to Markdown converters, so they are different to this project, there is no Markdownify in the JS world that I'm aware of.
A better name could be WYMIWYG, "What you markdown is what you get" :P