Changed environment variable behavior to accept comma separated models rather than a JSON encoded value

src/Keybert/Program.php

@@ -30,6 +30,14 @@
             else
             {
                 $preload = getenv('KEYBERT_PRELOAD');
+                if($preload === false || $preload == '')
+                {
+                    $preload = null;
+                }
+                else
+                {
+                    $preload = explode(',', $preload);
+                }
             }
 
             $keybert = new Keybert($preload, null, $port);