Fix link to official MIDI specifications

Author: Geokureli

README.md

@@ -9,7 +9,7 @@ A framework for producing test MIDI files
 See also:
 - [**midi-test**](https://github.com/jazz-soft/midi-test)
 - [**web-midi-test**](https://github.com/jazz-soft/web-midi-test)
-- [**official MIDI specifications**](https://www.midi.org/specifications)
+- [**official MIDI specifications**](https://midi.org/specs)
 
 ## Before use
 Please run `npm install` to make sure all dependencies are up to date.