[Feature Request] Ability to use with your own code instead of just a command line tool

[ahsan-a]

It would be really useful if you could use it as a function where you pass in your markdown content as a string in a function from within your code, instead of using it from the command line. Many things now use markdown, and the ability to integrate this package into a node project would be very useful.

[ephraimduncan]

I will export the renderMarkdown function for use as a library so that it can be imported and not use only as a cli