Add BLE MIDI transport (feature_bluetooth)

include/app_task.h

@@ -2,6 +2,7 @@
 
 #include <cstdint>
 #include "midi_transport.h"
+#include "ble_midi_transport.h"
 #include "led_stub.h"
 #include "switch_stub.h"
 
@@ -14,7 +15,7 @@ struct PadMapping {
 
 class AppTask {
 public:
-    AppTask(LedStub* led, SwitchStub* sw, UsbMidiTransport* midi);
+    AppTask(LedStub* led, SwitchStub* sw, UsbMidiTransport* usb_midi, BleMidiTransport* ble_midi = nullptr);
     
     void begin();
     void update();
@@ -23,7 +24,8 @@ public:
 private:
     LedStub* led_driver;
     SwitchStub* switch_driver;
-    UsbMidiTransport* midi_transport;
+    UsbMidiTransport* usb_midi;
+    BleMidiTransport* ble_midi;
     
     static const uint8_t NUM_PADS = 10;
     PadMapping pad_mapping[NUM_PADS];