Allow Offset for sensors

[kaylemstyx2020]

Add an option to add an offset to the sensor. so if the persons blood sugars are 5.0 but the sensor detects 4.0. Add an option to ofset it so it shows a more accurate level. This would come in handy for Automations where Notifications are sent to people when sugars are low or high as would allow for more accurate alerts as you would be aware of the difference.