Detect full charge and improve watchface display

src/displayapp/screens/WatchFaceAnalog.h

@@ -49,6 +49,7 @@ namespace Pinetime {
         uint8_t currentDay = 0;
 
         DirtyValue<uint8_t> batteryPercentRemaining {0};
+        DirtyValue<bool> isCharging {};
         DirtyValue<std::chrono::time_point<std::chrono::system_clock, std::chrono::nanoseconds>> currentDateTime;
         DirtyValue<bool> notificationState {false};
 
@@ -81,6 +82,7 @@ namespace Pinetime {
         Controllers::Settings& settingsController;
 
         void UpdateClock();
+        void SetBatteryIcon();
 
         lv_task_t* taskRefresh;
       };