advertise the correct MediaType when transcoding

some TVs fail if you send a Content-Type of the source file (matroska) follow by a transcoded body (mpeg ts)

cmd/go2tv-lite/go2tv.go

@@ -137,6 +137,10 @@ func run() error {
 		absMediaFile = *urlArg
 	}
 
+	if *transcodePtr && strings.Contains(mediaType, "video") {
+		mediaType = "video/vnd.dlna.mpeg-tts"
+	}
+
 	absSubtitlesFile, err := filepath.Abs(*subsArg)
 	if err != nil {
 		return err

cmd/go2tv/go2tv.go

@@ -136,6 +136,10 @@ func run() error {
 		absMediaFile = *urlArg
 	}
 
+	if *transcodePtr && strings.Contains(mediaType, "video") {
+		mediaType = "video/vnd.dlna.mpeg-tts"
+	}
+
 	absSubtitlesFile, err := filepath.Abs(*subsArg)
 	if err != nil {
 		return err

internal/gui/actions.go

@@ -339,6 +339,10 @@ func playAction(screen *FyneScreen) {
 		}
 	}
 
+	if screen.Transcode && strings.Contains(mediaType, "video") {
+		mediaType = "video/vnd.dlna.mpeg-tts"
+	}
+
 	if screen.SelectInternalSubs.Selected != "" {
 		for n, opt := range screen.SelectInternalSubs.Options {
 			if opt == screen.SelectInternalSubs.Selected {