Document that "is required($reason)" is also possible

Author: lizmat

doc/Type/Attribute.pod6

@@ -62,6 +62,15 @@ error.
     CATCH{ default { say .^name, ': ', .Str } }
     # OUTPUT: «X::Attribute::Required: The attribute '$!a' is required, but you did not provide a value for it.␤»
 
+You can also specify a reason why the attribute is required:
+
+    class D {
+        has $.a is required("it is a good idea");
+    }
+    my $d = D.new;
+    CATCH{ default { say .^name, ': ', .Str } }
+    # OUTPUT: «X::Attribute::Required: The attribute '$!a' is required because it is a good idea,␤but you did not provide a value for it.␤»
+
 =head2 X<trait is DEPRECATED|trait,is DEPRECATED (Attribute)>
 
     multi sub trait_mod:<is>(Attribute:D $r, :$DEPRECATED!)