DOC: Update doc with new MPD link

README.md

@@ -139,6 +139,6 @@ Please, refer to the [CONTRIBUTING](CONTRIBUTING.md) file.
 ## MPD
 
 Lektor is almost MPD compatible, at least it uses the same protocol, which can
-be consulted [here](https://www.musicpd.org/doc/html/protocol.html#). The full
-support for MPD clients (like mpc and ncmpc) is still WIP. For the MPD
+be consulted [here](https://mpd.readthedocs.io/en/stable/protocol.html). The
+full support for MPD clients (like mpc and ncmpc) is still WIP. For the MPD
 compatibility list, see the [CONTRIBUTING](CONTRIBUTING.md) file.