no click detection

There is only Clicked in this enum (focus.rs)
```
pub enum Interaction {
/// The node has been clicked
Clicked,
/// The node has been hovered over
Hovered,
/// Nothing has happened
None,
}
```
Any query with that is called in every frame. I want an event that is only called exactly once in the first frame when the btton is clicked firstly. Otherwise I have to add bookkeeping about the mouse state