doc: add lambda and call-operator sample code

doc/sample/Blocks.im

@@ -0,0 +1,14 @@
+pkg2 = {
+    onEnter => [
+        cout put:'start!'
+    ],
+
+    onExit => [
+        cout put:'end!'
+    ]
+}.
+
+
+x = a(x:5 y:2) + 5.
+a + b().
+a->b().