cmd/streamdata: format mirror field

This is useful for referring to the corresponding YouTube video.

Signed-off-by: Yonah <contrib@gensokyo.uk>

cmd/streamdata/format.go

@@ -18,4 +18,7 @@ func printVOD(v *streamdata.VOD) {
 	} else {
 		fmt.Printf("YouTube  : %s | %s\n", v.Title, date)
 	}
+	if v.Mirror != "" {
+		fmt.Println("Mirror   :", v.Mirror)
+	}
 }