add recursive calculation of a fibonacci number

examples/recursive.ang

@@ -0,0 +1,15 @@
+
+/*
+# fibonacci sequence
+func fib(n) {
+    if n <= 1 {
+        return n
+    }
+
+    return fib(n - 1) + fib(n - 2)
+}
+
+write(fib(4))
+*/
+
+write("test")