FR: For cover/shutter, add buttons with preset shutter positions

[doron1]

Here's a "would be neat" feature:
When you long press a cover entity, you get a panel with open and close buttons, and a slider to set to an arbitrary position. It would be neat if I could add a button or two, with a preset shutter position (e.g. 37%). Some shutters allow for a specific middle position that basically means "shutter down but allows light in", which such a button will make easy to go to.

Thinking about it, it would be nice for a dimmer as well.