Minor change to Numrush

Honestly I don't know if this warrants an update but here we go: I have deployed a new build with two changes:

- caps Numrush additional time to 6 seconds (it was brought to my attention that it was too easy to get 20 seconds otherwise)
- adds #GNUTerryPratchett easter egg. Not easy to trigger (it took me 30 minutes and I was in debug mode!) but worth it, if you can make it. Also, worth adding it because Terry Pratchett.

Also, I took the chance and made a Let's Play video (ahah) because I'm told it's a good idea