main: Add empty battery screen

This disables low battery monitor shutdown (LBM shutdown) on boot and checks if battery is enough.

The logic is as follows:

If battery is not enough:
- If not charging and 15s pass, it will re enable LBM shutdown and power off.
- If charging, it will wait until it is charged above the limit.
 Screen will auto turn off to save power. A press on Power button or a change on charger, will enable it for another 15s.

If battery is enough:
- Enables LBM shutdown and continues with the boot process.

bootloader/power/max7762x.h

@@ -113,6 +113,6 @@ int max77620_regulator_set_voltage(u32 id, u32 mv);
 int max77620_regulator_enable(u32 id, int enable);
 int max77620_regulator_set_volt_and_flags(u32 id, u32 mv, u8 flags);
 void max77620_config_default();
-void max77620_low_battery_monitor_config();
+void max77620_low_battery_monitor_config(bool enable);
 
 #endif