Added cancel button in buttons list

AppCore.cpp

           , m_pBtnOk(new Button{PIN_BTN_OK})
           , m_pBtnMinus(new Button{PIN_BTN_MINUS})
           , m_pBtnPlus(new Button{PIN_BTN_PLUS})
-          , m_pButtons{m_pBtnOk, m_pBtnMinus, m_pBtnPlus}
+          , m_pButtons{m_pBtnCancel, m_pBtnOk, m_pBtnMinus, m_pBtnPlus}
           , m_pLcd(new LiquidCrystal{PIN_LCD_RS, PIN_LCD_ENABLE, PIN_LCD_D4, PIN_LCD_D5, PIN_LCD_D6, PIN_LCD_D7})
           , m_pOneWire(new OneWire{PIN_ONEWIRE})
           , m_pSensors(new DallasTemperature{m_pOneWire})

AppCore.h

     Button* m_pBtnOk;
     Button* m_pBtnMinus;
     Button* m_pBtnPlus;
-    Button* m_pButtons[3];
+    Button* m_pButtons[4];
 
     LiquidCrystal* m_pLcd;