Optional__Cell-grid height (LDtk's __cHei, falls back to cHei).
Optional__Cell-grid width (LDtk's __cWid, falls back to cWid).
OptionalcAlternate height key.
OptionalcAlternate width key.
Row-major flat array of int values (0 = empty).
Subset of an LDtk IntGrid layer instance needed for grid extraction.