Add animation to the OSD

## Feature Description

Add animation to ensure the slider moves smoothly.
## Use Case
https://github.com/user-attachments/assets/a8df72ce-b8aa-4775-8c12-0d3e4cab9cbf

## Compositor

Is this feature specific to one compositor?

- [x] All compositors
- [ ] niri
- [ ] Hyprland
- [ ] dwl (MangoWC)
- [ ] sway

## Proposed Solution
For example, add the following code to DankSlider:
```
Behavior on value {
NumberAnimation {
duration: 100
easing.type: Easing.OutCubic
}
}
```