not anything new, just a minor fix to an html syntax error

Okay, slight update since Neocities didn't make it a separate update. The "play-in-browser" page for Chex 3 Vanilla's site has been updated to use a newer version of js-dos. Make sure to clear your browser cache.

Also, please don't open dosframe.html directly: That's just a workaround for CSS conflict nonsense in the newer version of js-dos. Use "chex3v/play.html" instead.