Fix for VTT writer

Doesn't support <br/> tags

MediaBrowser.MediaEncoding/Subtitles/VttWriter.cs

@@ -19,7 +19,7 @@ namespace MediaBrowser.MediaEncoding.Subtitles
                     cancellationToken.ThrowIfCancellationRequested();
 
                     writer.WriteLine(@"{0:hh\:mm\:ss\.fff} --> {1:hh\:mm\:ss\.fff}", TimeSpan.FromTicks(trackEvent.StartPositionTicks), TimeSpan.FromTicks(trackEvent.EndPositionTicks));
-                    writer.WriteLine(trackEvent.Text);
+                    writer.WriteLine(trackEvent.Text.Replace("<br />", "\r\n"));
                     writer.WriteLine(string.Empty);
                 }
             }