Added docs for Setty.default

Author: Jan-Olof Hendig

doc/Type/Setty.pod6

@@ -104,6 +104,24 @@ The number of elements of the set.
 The total of all the values of the C<QuantHash> object. For a C<Setty>
 object, this is just the number of elements.
 
+=head2 method default
+
+Defined as:
+
+    method default returns False
+
+Returns the default value of the invocant, i.e. the value which is returned
+when trying to access an element in the C<Setty> object which has not been
+previously initialized or when accessing an element which has explicitly
+been set to C<Nil> or C<False>.
+
+    my $s1 = SetHash.new(1, 2, 3);
+    say $s1{2};                                           # True
+    $s1{2} = Nil;
+    say $s1{2};                                           # False
+    # access non initialized element
+    say $s1{4};                                           # False
+
 =head2 method ACCEPTS
 
     method ACCEPTS($other)