Maps: Option to bold the outline of the fixed cells at the beginning of the game

[xina-rose]

Is your feature request related to a problem? Please describe.
I sometimes forget what the fixed, starting cells were after I've colored in other cells, because there is no visual difference between the starting cells and the ones I've colored in based on inferences. Being able to see the fixed starting cells would help me check my inferences.

Describe the solution you'd like
An option to increase the line weight of the borders of the fixed, starting cells, in order to visually differentiate them from the ones you fill in yourself would be helpful.

Describe alternatives you've considered
You could also do a dashed line, or any pattern line you want. But I think an option to bold the starting cells could be a good solution.

Additional context
I really like your game. I am starting to see the patterns. I am high.