extra class code and readme update

Author: Evan Willhite

README.md

@@ -1,25 +1,33 @@
 # bem-twig-extension
-Twig function that inserts static classes into Pattern Lab but adds them to the attributes object in Drupal
+Twig function that inserts static classes into Pattern Lab but adds them to the Attributes object in Drupal
 
-## Usage
+## Usage (4 arguments)
 
-#### Simple block name:
-`<h1{{ bem('title') }}>`
+#### Simple block name (required argument):
+`<h1 {{ bem('title') }}>`
 
 This creates:
 
 `<h1 class="title">`
 
-#### Block with modifiers (array allowing multiple modifiers):
-`<h1{{ bem('title', ({1: 'small', 2: 'red'})) }}>`
+#### Block with modifiers (optional array allowing multiple modifiers):
+`<h1 {{ bem('title', (['small', 'red'])) }}>`
 
 This creates:
 
 `<h1 class="title title--small title--red">`
 
-#### Element with modifiers and blockname:
-`<h1{{ bem('title', ({1: 'small', 2: 'red'}), 'card') }}>`
+#### Element with modifiers and blockname (optional):
+`<h1 {{ bem('title', (['small', 'red']), 'card') }}>`
 
 This creates:
 
 `<h1 class="card__title card__title--small card__title--red">`
+
+#### Element with modifiers, blockname and extra classes (optional - in case you need non-BEM classes):
+
+`<h1 {{ bem('title', (['small', 'red']), 'card', (['js-click', 'something-else'])) }}>`
+
+This creates:
+
+`<h1 class="card__title card__title--small card__title--red js-click something-else">`

bem.function.php

@@ -6,7 +6,7 @@
 
 use Drupal\Core\Template\Attribute;
 
-$function = new Twig_SimpleFunction('bem', function ($context, $base_class, $modifiers = array(), $blockname = '') {
+$function = new Twig_SimpleFunction('bem', function ($context, $base_class, $modifiers = array(), $blockname = '', $extra = array()) {
   $classes = [];
 
   // If using a blockname to override default class.
@@ -33,6 +33,13 @@
     }
   }
 
+  // If extra non-BEM classes are added.
+  if (isset($extra) && is_array($extra)) {
+    foreach ($extra as $extra_class) {
+      $classes[] = $extra_class;
+    };
+  }
+
   if (class_exists('Drupal')) {
     $attributes = new Attribute();