This is awesome. Glad to see there's still life and interest in this project. Is there a README or documentation on the additional functionality?

@utdrmac No not yet. The options are (with defaults):

const defaults = {
  sourceUrl: null,
  ratio: '4:3',
  highlightStyle: 'default',
  highlightLines: false,
  highlightSpans: false,
  highlightInlineCode: false,
  highlightLanguage: '',
  slideNumberFormat: '%current% / %total%',
  cloneTarget: '_blank',
  excludedClasses: [],
  countIncrementalSlides: true,
  macros: {},
  transition: false,
  transitionSpeed: false,
  slideNumber: false,
  progressBar: false,
  controls: false,
  controlsTutorial: false,
  controlsLayout: 'bottom-right',
  controlsBackArrows: 'faded',
  folio: false,
  allowControl: true,
  navigation: {},
  translations: {}
};

For the ported settings (controls, transition, progress bar), see https://github.com/hakimel/reveal.js/#configuration.
allowControl disable the controller, useful for the new function SlideShow::setState which allows you to set the state (current slide, pause, blackout, mirrored). SlideShow::getState returns the current state. folio false makes the presentation full screen, true is the old style.

Did you upgrade to the most recent version of marked or did you possibly switch to using CommonMark?

Edit: Sorry I over read the that you asked for the update of marked. No I don't.

I updated to marked 0.4.0, options for marked can be set using marked: {...} for the options.

I'm not a github/git guru. What's the best way to test this PR?

I made an archive for you: https://github.com/GM-Alex/remark/releases/download/es6-rework/remark-es6.zip

I also add an easy way to use columns just use || as separator and it will make a new column at the same slide.

@GM-Alex That's great works. Since the author has dropped maintenance of remarkjs, could you contact the author to transfer this project to you?

I made a simple test, find that when sourceUrl set with a markdown file, I get these errors:

Uncaught TypeError: r.open is not a function
    at a.value (remark.min.js:1)
    at a.value (remark.min.js:1)
    at a.value (remark.min.js:1)
    at a.value (remark.min.js:1)
    at new a (remark.min.js:1)
    at e.value (remark.min.js:1)
    at (index):10