feathers: Widgets should document which events they emit

[torsteingrindvik]

How can Bevy's documentation be improved?

The controls here:

https://dev-docs.bevy.org/bevy/feathers/controls/index.html

For example button:

https://dev-docs.bevy.org/bevy/feathers/controls/fn.button.html

should specify in docs which event (or events) they emit when interacted with.

Currently the only way to know is to look at the feathers example to see which events are observed close to some control, for example: On<ValueChange<bool>>, On<Activate>, On<ValueChange<f32>>, etc.

Ideally each control had a snippet in the docs to the effect of

// From the feathers example, a relatively minimal snippet of how to observe checkbox interactions
(
    checkbox(
        InteractionDisabled,
        Spawn((Text::new("Disabled"), ThemedText))
    ),
    observe(|_change: On<ValueChange<bool>>| {
        warn!("Disabled checkbox clicked!");
    })
),