Make AnimatableSlider inherit from UISlider and add designable images

[phimage]

AnimatableSlider do not extends UISlider, only UIView

thumb, minimum and maximum track images added has designable objects in storyboard

PS:
I try some experiment on slider size by overriding trackRect()

 @IBInspectable var trackHeight: CGFloat = CGFloat.nan
    
    override func trackRect(forBounds bounds: CGRect) -> CGRect {
       // add here if not trackHeight.isNan
        return CGRect(origin: bounds.origin, size: CGSize(width:bounds.width, height:trackHeight))
    }
 // or
    override func trackRect(forBounds bounds: CGRect) -> CGRect {
       let rect = super.trackRect(forBounds: bounds)
       return ...
    }

There is some bug when using maximum and minimum images
to fix some other bugs in storyboard I use in trackRect()

#if TARGET_INTERFACE_BUILDER
 // do some stuff to adjust storyboard
#endif

[IBAnimatableBot]

	1 Warning
⚠️	Consider adding supporting documentation to this change. Documentation can be found in the docs directory.

Generated by 🚫 Danger

[JakeLin]

I like you PR very much with a lot of documentation comments 👍👍👍. I think this PR is ready to go. It will be greate if you can modify the CHANGELOG.md file. It is very simple like https://github.com/IBAnimatable/IBAnimatable/blob/master/CHANGELOG.md#enhancements

One thing I need to confirm with @tbaranes on why did we inherit from UIView. If he is OK, we will merge it. Thanks again 💪

[JakeLin]

I think we need to make it public for the others can use those extension methods outside of IBAnimatable framework.

[JakeLin]

Shall we remove all self?

[tbaranes]

+1, also all the others below 😬

[JakeLin]

@phimage thank you very much for your PR. Please have a look at my small comments.

@tbaranes In #228, we created AnimatableSlider. I know we want to have fully customizable AnimatableSlider and UISlider can't give us that 😕. Therefore, we let it inherit from UIView instead of UISlider. @phimage found out that and made AnimatableSlider to inherit from UISlider. I think that is better for now since the current AnimatableSlider is more like AnimatableView.

If we want to have fully customizable AnimatableSlider in the future, we may create another class like AnimatableCustomSlider to inherit from UIView. Can I have your opinion on this PR? thanks.

[tbaranes]

+1, also all the others below 😬

[tbaranes]

I agree with you @JakeLin, that PR is a good move since it's making AnimatableSlider more slider. I don't really remember why we choose UIView instead of UISlider in #228, but I can't see any reasons. Truth is when we will do the custom sliders, it won't really be related to AnimatableSlider, so... who cares?

@phimage Good job on this!

[phimage]

Ok for the changes (public and self)
For changelog I make two lines? one in "api breaking changes" or not?

I will fix also some changelog issue with markdown comma

[JakeLin]

@phimage well done. It is in 🎉, thanks a lot. It will be in version 4. @tbaranes thanks for your feedback.