Addition of time based valve, similar to time based cover

I am using a valve with 3 wires: 2 wires to control direction and a common neutral. Powering one wire turns the motor one way, power on the other turns the other way. I am using a Sonoff Dual to control the wires. The current setup is using[ time based cover](https://esphome.io/components/cover/time_based); it takes 16 seconds to close or open in my case; the component estimates the position based on run time. Of course there is some drift but that does not really matter; valve is closed every now and then to reset the position.

It would be nice to have a time based [valve component](https://esphome.io/components/valve/) as well; I guess that there are more valves out there that work on this principle (more than there are affordable valves with true position feedback).

Start by comparing the linked time-based cover component with the linked valve component and review how the Sonoff Dual's two direction wires and common neutral are represented. Done means a documented time-based valve option can estimate position from run time, support opening and closing, and periodically reset at the closed position.

Written by the indexing model from the issue text.