status_led sharing with output

[dattas]

Describe the problem you have/What new integration you would like

With sonoffs where it only has a single LED it would be nice to be able to use status_led and also use the single LED as a monochromatic light for current status of the relay.

Please describe your use case for this integration and alternatives you've tried:

Knowing the status of the relay is nice for user feedback at a glance, however when setting up both a light and a status_led, the status_led component overwrites the status every loop. Behavior in https://github.com/esphome/esphome-core/blob/dev/src/esphome/status_led.cpp#L30 . An I had to implement the idea would be to have the monochromatic light platform be able to output the desired values to the status_led component and instead of writing false if the status is good, write whatever the desired value is.

Additional context
Here is an example for a sonoff that I'm currently using: https://gist.github.com/dattas/1549af84e273cdf673d750fb46607694