Merging dev branch 2.9.4

[alvarotrigo]

• Fixed bug: afterLoad always fires first index=1 even accessing the page on any other section afterLoad always fires first index=1 even accessing the page on anchor=3 #2519
• Fixed bug: resizing viewport pauses media elements on slides Resize browser = video pauses (only on second slide and upward) #2471 Autoplay video/audio stops when a section is firing fitToSection  #2526
• Fixed bug: direct URL links wouldn't work when using an active slide for page load External links with active section and active slide? #1646
• Added: new method fitToSection() New method fitToSection() ?  #2575
• Added: lazy load for elements using srcset Lazy load for picture element/srcset/sizes #2355