Add ceiling division operation to the Math.sol library (#2681)

Co-authored-by: Hadrien Croubois <hadrien.croubois@gmail.com>
Co-authored-by: Francisco Giordano <frangio.1@gmail.com>

contracts/mocks/MathMock.sol

@@ -16,4 +16,8 @@ contract MathMock {
     function average(uint256 a, uint256 b) public pure returns (uint256) {
         return Math.average(a, b);
     }
+
+    function ceilDiv(uint256 a, uint256 b) public pure returns (uint256) {
+        return Math.ceilDiv(a, b);
+    }
 }