Enable check counting for rookmate

Closes #979.

Author: ianfab

src/variants.ini

@@ -581,7 +581,7 @@ promotionRegionWhite = *6
 doubleStep = false
 
 #https://www.chess.com/variants/rookmate
-[rookmate:chess]
+[rookmate:3check]
 #in this variant, one rook is royal, one isn't
 #to define this, the royal rook will be a king(K) with custom moves, and the non-royal king a commoner(C)
 pieceToCharTable = PNBRQC...............Kpnbrqc...............k