[Feature Request] Slider: add support for monitoring `Release` SliderEvent

[Jordan-Haidee]

Currently, the Slider component only supports listening to the Change event [link]:

pub enum SliderEvent {
    Change(SliderValue),
}

It would be great to add support for a Release event as well (just like that in Slint), so a custom callback can be triggered when the user releases the slider thumb. This is especially useful in scenarios like music or video players.

Ideally, the API could look like this:

pub enum SliderEvent {
    Change(SliderValue),
    Release(SliderValue),
}