Add support for monitor point

[khenderick]

The Reolink app supports a Monitor Point on certain cameras (e.g. E1 Pro). This point is a "saved PT position". With the push of a button, I can set the current PT position as new Monitor Point or can move the camera back to the previously saved Monitor Point. I can also instruct the camera to automatically move back to the Monitor Point after a set amount of time

I'd love to use MQTT to configure the auto-return and auto-return interval, and have MQTT commands available to set the current position as new Monitor Point and to return to it.