Update variant.h

commitGates is Musketeer Chess Gating mechanic. Ultimately commitGates should be renamed musketeerGating

src/variant.h

@@ -109,6 +109,7 @@ struct Variant {
   WallingRule wallingRule = NO_WALLING;
   Bitboard wallingRegion[COLOR_NB] = {AllSquares, AllSquares};
   bool seirawanGating = false;
+  bool commitGates = false;
   bool cambodianMoves = false;
   Bitboard diagonalLines = 0;
   bool pass[COLOR_NB] = {false, false};