Fix subtitle encoder if subrip is requested

MediaBrowser.MediaEncoding/Subtitles/SubtitleEncoder.cs

@@ -294,7 +294,7 @@ namespace MediaBrowser.MediaEncoding.Subtitles
                 return true;
             }
 
-            if (string.Equals(format, SubtitleFormat.SRT, StringComparison.OrdinalIgnoreCase))
+            if (string.Equals(format, SubtitleFormat.SRT, StringComparison.OrdinalIgnoreCase) || string.Equals(format, "subrip", StringComparison.OrdinalIgnoreCase))
             {
                 value = new SrtWriter();
                 return true;