Meta data description: Grammar, and Spelling Fixes.

[MikeStirner]

1. "You can use it to relax or to solve difficult grids to your opinion."
   Change to: You can use it to relax or to solve difficult grids. Whatever you prefer.

2. "difficulty (covering a incresing number of game variants)"
   Change to: difficulty (covering an increasing number of game variants)

[meikpiep]

Fixed and committed in the next minutes, including suggested changes of @HarmfulBreeze contained via comment at Weblate https://hosted.weblate.org/translate/gauguin/gauguin-metadata/en_US/?q=has:comment#comments:

Shouldn't "usage of single cells" be "usage of single cages"? Also bullet points should probably be em-dashes instead of minuses.

Thanks for the optimizations! If you have faith in optimizing or rewriting the description, let me know.