<!— Container that holds slides.
PhotoSwipe keeps only 3 of them in the DOM to save memory.
Don't modify these 3 pswp__item elements, data is added later on. —>
<!— Default (PhotoSwipeUI_Default) interface on top of sliding area. Can be changed. —>
<!— Controls are self-explanatory. Order can be changed. —>
<!— Preloader demo http://codepen.io/dimsemenov/pen/yyBWoR —>
<!— element will get class pswp__preloader--active when preloader is running —>