Adding time-based options to cover template

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

I'd like to have a time-based cover that gets its state verified at each end.
**Please describe your use case for this integration and alternatives you've tried:**

I would like for my template cover to provide additional close percentage information to HASS.
**Additional context**

I have no problem with implementing this but I will need a bit of guidance on how to get started. I haven't been actively developing C++ in the last few years.