Added ‘setSegmentLength’ to README.md

Author: pascalbaljet

README.md

@@ -150,6 +150,7 @@ $highBitrate = (new X264)->setKiloBitrate(1000);
 FFMpeg::fromDisk('videos')
     ->open('steve_howe.mp4')
     ->exportPlaylistForHLS()
+    ->setSegmentLength(10) // optional
     ->addFormat($lowBitrate)
     ->addFormat($midBitrate)
     ->addFormat($highBitrate)