blazy 8.x-1.0-beta2

A couple of fixes and integration issues.

• Added default sizes.
• Removed redundant Preloader option since the classes are within image containers. Maybe more reasonable for Views later which can text, images, etc.
• Added support for non-lazyloaded images such as Slick carousel.
• Fixed for Overlays regression.
• #2719541: Fallback to default Media entity thumbnail when Main image empty.
• Fixed for broken Image to iframe switcher by previous updates.
• #2719541: Fallback to default Media entity thumbnail when Main image empty.
• Fixed for Undefined index: target_bundles when accessing Media entity field options from within Views UI.
• #2716765: Map or rework breakpoints into srcset as per v1.6.0
• Removed Retina option since it is now possible with SRCSET descriptors.
• Added aspect ratio support for multi-breakpoint images.
• Made efficient blazy_preprocess_field().
• Fixed for media_iframe typo, should be media__iframe.