add formatter methods for next/previous mode

lib/MiLight/PacketFormatter.cpp

@@ -38,6 +38,8 @@ void PacketFormatter::updateBrightness(uint8_t value) { }
 void PacketFormatter::updateMode(uint8_t value) { }
 void PacketFormatter::modeSpeedDown() { }
 void PacketFormatter::modeSpeedUp() { }
+void PacketFormatter::nextMode() { }
+void PacketFormatter::previousMode() { }
 void PacketFormatter::command(uint8_t command, uint8_t arg) { }
 
 void PacketFormatter::updateHue(uint16_t value) { }

lib/MiLight/PacketFormatter.h

@@ -36,6 +36,8 @@ public:
   virtual void updateMode(uint8_t value);
   virtual void modeSpeedDown();
   virtual void modeSpeedUp();
+  virtual void nextMode();
+  virtual void previousMode();
   
   virtual void pair();
   virtual void unpair();