implement new chess variations chess960x4x2 and chess4x2 like described in https://github.com/topce/chess960x4x2

[topce]

implement new chess variations like described in https://github.com/topce/chess960x4x2 Enhance lichess to support new chess pieces Hawk ( moves like Knight and Bishop ) Elephant ( moves like Knight and Rook ) Amazon ( moves like Knight ,Bishop and Rook ) implement chess960x4x2 and chess4x2

[ornicar]

we're not adding new variants