for flexible format support

```
JSV::Validator->new(
    format_support => +{
        original_format => sub {
            my $instance = shift;
            return $instance eq "omoro-";
        }
    }
);
```

or

```
$jsv_instance->register_format("original_format", sub {
    my $instance = shift;
});
```

みたいな感じで。