Fix Attack Command Number; Add Chorus & Portamento Time

- Fixed ATTACK_TIME value
- Added CHORUS value
- Added PORTAMENTO_TIME to match the PORTAMENTO on/off value

Author: deckerego

adafruit_midi/control_change_values.py

@@ -46,13 +46,15 @@
 EXPRESSION = 11
 SUSTAIN_PEDAL = 64
 PORTAMENTO = 65
+PORTAMENTO_TIME = 37
 FILTER_RESONANCE = 71
 RELEASE_TIME = 72
-ATTACK_TIME = 74
+ATTACK_TIME = 73
 CUTOFF_FREQUENCY = 74
 DECAY_TIME = 75
 VIBRATO_RATE = 76
 VIBRATO_DEPTH = 77
 VIBRATO_DELAY = 78
+CHORUS = 93
 ALL_CONTROLLERS_OFF = 121
 ALL_NOTES_OFF = 123