doc: add really simple source file for parser testing

doc/sample/Simple.im

@@ -0,0 +1,14 @@
+package simple.pkg
+
+use std.io
+
+class Simple
+    - init(name:name age:age)
+        self::name = name.
+        self::age = age!
+
+    - name | ^self::name.
+
+    - age
+        ^self::age!
+end