[Feature Request] Add button domain

[sibbl]

Is your feature request related to a problem? Please describe.
I'd love to have an easy way to expose button entities.

Describe the solution you'd like
In my specific case, the Roborock extension offers button entities to trigger specific cleaning routines. I'd love to simply expose them without having to wrap them in scenes or switches or input booleans.

[Luligu]

Hi,
sorry but a little bit more of context is needed.

[sibbl]

Maybe this PR provides the necessary context? sibbl#1

Still untested, hence no PR to this repo yet.

I’d love to get some feedback first if button maybe was left out intentionally, and only script, input_button, … are converted accordingly.