As @cronopios mentions, if you need a bit of flexibility in the output, you need to use a wrapper over Chromium — either Electron, or (the more recent) Puppeteer.
Other than that, it runs the article through Readability to extract just the main content and applies customizable CSS / HTML to it.
Had a great time at the first edition of the meetup.. Met some interesting people and it's always great to talk to fellow HN'ers in person.. Also need to mention the Pizza & Beer treat we had.. ( pretty much the standard geek ration)