Loading spinners for carrousel mode

[KrlLevchenko]

I'm submitting a...

[ ] Regression (a behavior that used to work and stopped working in a new release)
[ ] Bug report  
[x] Feature request
[ ] Documentation issue or request
[ ] Support request

Current behavior

There is no way to use spinner (loading indicator) when using carrousel. If I use modal gallery I see spinner and that is ok but there is no any spinners for carrousel mode I need this because I have multiple galleries and I'm switching between them.

// Gallery is my own class from backend containing links to photos
public select(gallery: Gallery){
    this.selectedImages = gallery.images.map((p, i) =>
      new Image(i, {
          img: p.url,
          extUrl: p.url,
          description: ''
        },
        {
          img: p.previewUrl
        }
      )
    );
  }

And I see old photos some time after selecting new gallery

Expected behavior

I see spinner while all images not loaded

Environment (the most important section to fill very carefully)

- @ks89/angular-modal-gallery version: 7.2.7
- Node version: 12.16.1
- npm version: 6.13.4



Browser:
- [x] Chrome (desktop) version 90.0.40
- [ ] Chrome (Android) version XX
- [ ] Chrome (iOS) version XX
- [ ] Firefox version XX
- [ ] Safari (desktop) version XX
- [ ] Safari (iOS) version XX
- [ ] IE version XX
- [ ] Edge version XX

Others:

[Ks89]

Hi! Loading spinners in Carousel is still not implemented.