Request: action to mark invalid fields in Tents

[thinkedem]

I’d like to request an action for the Tents game, that would mark every square that are not next to a tree as empty, cause it’s trivial that no tents can go there, but on larger sizes it an be a chore to manually mark them all up. Fields that have a tree next to them (orthogonally) would not be marked even in rows or columns with 0 tents of course, only fields that can not orthogonally next to a tree.