<feature> Add docs to explain how to customize form_theme layout. Issue

#39

README.md

@@ -159,6 +159,7 @@ If the assetic bundle is installed but you don't want the AdminThemeBundle to us
 * [Sidebar User](Resources/docs/sidebar_user.md)
 * [Sidebar Navigation](Resources/docs/sidebar_navigation.md)
 * [Breadcrumb Menu](Resources/docs/breadcrumbs.md)
+* [Form theme](Resources/docs/form_theme.md)
 
  [1]: https://almsaeedstudio.com/themes/AdminLTE/documentation/index.html
  [2]: https://img.shields.io/badge/Symfony-%202.x%20&%203.x-green.svg

Resources/docs/form_theme.md

@@ -0,0 +1,38 @@
+## form-theme
+
+This bundle provide a form-theme under [Resources/views/layout/form-theme.html.twig](Resources/views/layout/form-theme.html.twig) which
+allow customize the form elements in AdminTLE.
+
+This is used as:
+
+```twig
+{% form_theme form 'AvanzuAdminThemeBundle:layout:form-theme.html.twig' %}
+```
+
+For override the default theme in twig template you need put in the template which you want the new form theme
+
+```twig
+{% form_theme form 'your-custom-form-theme-layout.html.twig' %}
+```
+
+For example:
+
+```twig
+{% form_theme form 'bootstrap_3_layout.html.twig' %}
+```
+
+You also could apply this, only checking if a form is defined:
+
+```twig
+{% if form is defined %}
+    {% form_theme form 'AvanzuAdminThemeBundle:layout:form-theme.html.twig' %}
+{% endif %}
+```
+
+Also is possible override the form theme by referencing 
+[multiple templates](http://symfony.com/doc/current/cookbook/form/form_customization.html#multiple-templates) in order of priority or
+only customize/override some childs elements in the form like:
+
+```twig
+{% form_theme form.submit 'AvanzuAdminThemeBundle:layout:form-theme.html.twig' %}
+```