[REQUEST] The possiblity to see how the subboard was won

[Nircek]

** Is your feature request related to a problem? Please describe. **
I'm always frustrated when I'm waiting for my opponent's move and then ... the subboard is won. And I don't know how was it possible. I guess my rival wasn't cheating but I have no idea how he won that part.

** Describe the solution you'd like **
I'm convinced the possibility to uncover the subboard after a click on it would be a very nice-looking and educative choice. And of course, after another click, the big winning mark should appear again. So the click on the won subboard would switch the viewing. One is a big won subboard (default) and another is how was it won.

** Describe alternatives you've considered **
There can be also some... gray or shaded uncovered subboard on the winning mark. Or the animation of striking out the three in a row. But I think the cover/uncover method is the most modern way and fits the app's design.

** Additional context **
Please consider the last move's mark.