LazyLoad loads all images on slider.mount

[Shau1a]

Hello!
Please help with LazyLoad setting.
v2 Splide has no such issue, but v3 Splide seems has some changes

Version

3.1.7

Description

I set next options to apply Lazy load:

lazyLoad: "nearby"
perPage: 1
preloadPages: 1
rewind: true
trimSpace: true
type: "fade"

slider structure is set according https://splidejs.com/guides/structure/ and each slide template looks like this:

<li class="splide__slide">
    <div class="splide__slide__container image-slide">
         <img alt="image" data-splide-lazy="image.jpg" height="100%" width="100%">
    </div>
</li>

on Slider.mount() all images are loaded without delay, they have src right after slider mounted and gets visible;
tested with different count of slides;

Also the issue with adding (secondarySlider.add(_sliderTemplate_);) new slides with data-splide-lazy: image is loaded but it has display: none; position: absolute; and stays not visible with running loader

Reproduction Link

No response

Steps to Reproduce

Case 1:

1. Create a new Splide instance
2. Add splide options lazyLoad: "nearby", preloadPages: 1, perPage: 1
3. Create template with data-splide-lazy instead of src for images
4. Check network after splide is visible -> all images already loaded

Case 2:

1. Create a new Splide instance
2. Add splide options lazyLoad: "nearby", preloadPages: 1
3. Create template with data-splide-lazy instead of src for images
4. Try to add dynamically slides with lazy loading (https://splidejs.com/guides/apis/#add)

### Expected Behaviour

Case 1:
Only first and second images are loaded and have src attribute, other images getting loaded with delay (after scroll to them)

Case 2:
New added images getting loaded only after scroll to them and then getting visible without display: none; style

Thank you in advise!

[NaotoshiFujita]

#461