Demo of Dark Mode Stylesheet for HN

I spent a pleasant couple of hours augmenting the Hacker News stylesheet to enable Dark Mode. There's a demo [here](https://github.com/rerdavies/hn_dark_mode/).

Obviously the changes don't do anything other than make a nice demo, unless somebody from Hacker News copies the modified stylesheet into HN production sources. So please upvote, in the hope that somebody from HN will notice.

No HTML has been modified in the production of this stylesheet (other than removing personal identification and auth tokens from the demo page).