You can add it. Just mention clearly on the game page that it was uploaded after the deadline. Say the truth and there are no problems. The Jam is to have fun between friends.
Viewing post in The Great Machine On Mars jam comments
The website doesn't allow this until the jam is over - I have posted a message on the jam forum asking about this so I'll wait to see if Javid replies. Until then, it's just provided as-is.
My apologies if it prevents people from playing the game.
This is my first jam so for next time I'll remember to leave more time for play testing (or at least ask someone else to try running it)!