Added example for var overloading

Simple example to demonstrate overloading in case technical lingo is confusing

doc/manual/type_rel.txt

@@ -294,6 +294,21 @@ If the formal parameter ``f`` is of type ``var T`` in addition to the ordinary
 type checking, the argument is checked to be an `l-value`:idx:. ``var T``
 matches better than just ``T`` then.
 
+.. code-block:: nim
+  proc sayHi(x: int): string =
+    # matches a non-var int
+    result = $x
+  proc sayHi(x: var int): string =
+    # matches a var int
+    result = $(x + 10)
+    
+  proc sayHello(x: int) =
+    var m = x # a mutable version of x
+    echo sayHi(x) # matches the non-var version of sayHi
+    echo sayHi(m) # matches the var version of sayHi
+
+  sayHello(3) # 3
+              # 13
 
 Automatic dereferencing
 -----------------------