Grid<E>.fromCells  constructor 
Creates a new ListGrid from elements in row-major order.
Each element in rows, a column, must have the same length, and the
resulting grid will have a width equal to the number of columns, and a
height equal to the length of each column.
The grid is initialized with the elements in the rows, where the element
at index (x, y) is rows.elementAt(y).elementAt(x). If the empty
element is omitted, the most common element in the rows is used, in which
case the rows must be non-empty.
Implementation
factory Grid.fromCells(
  Iterable<E> elements, {
  required int width,
  E? empty,
}) = ListGrid<E>.fromCells;