Input Group Button Support

[rdohms]

Added a new Extension to allow people to append buttons to inputs as well as
icons. Will add examples to the docs repo also. But this is what it looks
like:

$builder
           ->add('keywords', 'text', [
                   'label' => false,
                   'attr' => array(
                       'input_group' => array(
                           'button_append' => ['name' => 'search', 'type' =>
'submit']
                       )
                   )
               ]);

This closes #250.

[florianeckerstorfer]

Wow, thanks.

I am only thinking that it may would be better to use button instead of btn in the PHP and Twig names.

[rdohms]

I can do that, hang on.

[rdohms]

Done.

[rdohms]

Any other considerations?

[florianeckerstorfer]

Nope, this is great.

[psylosss]

Is it possible to set custom CSS-class to this appended button?

---

SOLVED: via options key, like 'options' => ['attr' => ['class' => 'btn btn-info']]