Shatranj premoves

package.json

@@ -1,6 +1,6 @@
 {
   "name": "chessgroundx",
-  "version": "10.6.2",
+  "version": "10.6.3",
   "description": "Extended lichess.org Chess UI",
   "type": "module",
   "module": "chessground.js",

src/premove.ts

@@ -208,7 +208,7 @@ function ferzOuk(color: cg.Color): Mobility {
     (color === 'white' ? x1 === 4 && y1 === 0 && x2 === 4 && y2 === 2 : x1 === 3 && y1 === 7 && x2 === 3 && y2 === 5);
 }
 
-// shatranj elephant
+// alfil (shatranj elephant)
 const elephant: Mobility = (x1, y1, x2, y2) => {
   const xd = diff(x1, x2);
   const yd = diff(y1, y2);
@@ -873,6 +873,29 @@ function builtinMobility(
         }
       };
 
+    case 'shatranj':
+      return (boardState, key, canCastle) => {
+        const piece = boardState.pieces.get(key)!;
+        const role = piece.role;
+        const color = piece.color;
+        switch (role) {
+          case 'p-piece': // pawn
+            return pawnNoDoubleStep(color);
+          case 'r-piece': // rook
+            return rook;
+          case 'n-piece': // knight
+            return knight;
+          case 'b-piece': // bishop
+            return elephant;
+          case 'q-piece': // queen
+            return ferz;
+          case 'k-piece': // king
+            return kingNoCastling;
+          default:
+            return noMove;
+        }
+      };
+
     case 'grand':
     case 'grandhouse':
       return (boardState, key) => {