Add Spotfy Support on Rekordbox 6.8.6

Since Alpha Theta removed License Unlock from some devices such as my DD‑RZX, and Rekordbox 7 does not work properly with this device, I feel harmed as a long‑time customer by these changes. Because of that, it would be very important and fair if you could add Spotify support to Rekordbox 6.8.6 as an old version that work fully my controller.