feat: Prompt for a score difference

[tomershvueli]

Hi!
Thanks for putting this scoreboard together! We had a TaskMaster party recently and used this scoreboard - people were amazed!

I did change one thing that made it easier to manage in an actual real-world setting: when clicking on scores, it opens up a prompt and asks for the difference in scores, instead of the total score. This means less math along the way :)

It looks like so:

One can also put in negative numbers if you messed up previously or want to adjust the scores.

Again, thanks so much for publishing this! I figured I'd offer this up as a change if it's interesting to you, but no worries if you want to leave it as is!

Thanks,

Tomer