feat: enable changing temperature with on button when light is on

[mgrove36]

Hi! Not sure if this is a feature others would find useful, so feel free to close it if not, but I like being able to adjust temperature from the dimmer. I've found the easiest way to do this is just to press the on button (when the light is already on, of course) - similar to how the v1 Philips Hue dimmers (below) work.

This PR changes the default functionality of the on button in the light-only blueprint to increment colour temperature when the light is turned on, instead of forcing the brightness level (if enabled, otherwise doing nothing). There are helper options for configuring max/min temperatures and the step to increment by. The change is handled by adding the step amount to the current temperature, unless the current temperature is greater than or equal to the maximum. Transition time can also be adjusted with a helper option.

This does however require that the light entity supports the color_temp attribute.

Thanks for your work on this blueprint - it's really useful!

[damru]

Hey,
This could be a good idea indeed 👍🏻, but this should be optional, same as for brightness forced value, as user doesn't necessarily want to loop over light temperature.