add supportBframes function

src/FFMpeg/Format/Video/Resamplable.php

@@ -30,9 +30,20 @@ interface Resamplable extends BaseVideo
      */
     public function getFrameRate();
 
+    /**
+     * Returns true if the current format supports B-Frames
+     *
+     * @see https://wikipedia.org/wiki/Video_compression_picture_types
+     *
+     * @return Boolean
+     */
+    public function supportBFrames();
+
     /**
      * Returns the GOP size
      *
+     * @see https://wikipedia.org/wiki/Group_of_pictures
+     *
      * @return integer
      */
     public function getGOPSize();