add benchmarks

benchmarks/montecarlo.ce

@@ -0,0 +1,11 @@
+var N = 10000000;
+var num = 0;
+for (var i = 0; i < N; i ++) {
+  var x = 2 * $_.random();
+  var y = $_.random();
+  if (y < Math.sin(x * x))
+    num++;
+}
+log.console(2 * num / N);
+
+$_.stop()