fixes BLE HID Battery Level Indicator (espressif#6864)

* fixes BLE HID Battery Level Indicator

* Fixing identation

Author: SuGlider

libraries/BLE/src/BLEHIDDevice.cpp

@@ -42,7 +42,10 @@ BLEHIDDevice::BLEHIDDevice(BLEServer* server) {
 
 	m_batteryLevelCharacteristic = m_batteryService->createCharacteristic((uint16_t) 0x2a19, BLECharacteristic::PROPERTY_READ | BLECharacteristic::PROPERTY_NOTIFY);
 	m_batteryLevelCharacteristic->addDescriptor(batteryLevelDescriptor);
-	m_batteryLevelCharacteristic->addDescriptor(new BLE2902());
+	BLE2902 *batLevelIndicator = new BLE2902();
+	// Battery Level Notification is ON by default, making it work always on BLE Pairing and Bonding
+	batLevelIndicator->setNotifications(true);
+	m_batteryLevelCharacteristic->addDescriptor(batLevelIndicator);
 
 	/*
 	 * This value is setup here because its default value in most usage cases, its very rare to use boot mode