check if a point lies on the curve in the tests

Signed-off-by: Uncle Fatso <uncle.fatso@ghostchain.io>

src/MathTester.sol

@@ -88,4 +88,8 @@ contract MathTester {
     function toAffineProjective(uint256 x, uint256 y, uint256 z) public pure returns (uint256, uint256) {
         return EllipticCurveProjective.toAffine(x, y, z);
     }
+
+    function isOnCurve(uint256 x, uint256 y) public pure returns (bool) {
+        return EllipticCurveProjective.isOnCurve(x, y);
+    }
 }