Add-ons Attachment Improvements By Xon 2.6.1

• Require XenForo 2.2+
• Require php 7.2+
• Improve drag&drop editor support. Thanks to @NamePros for sponsoring this feature.
  • Stock XenForo/Froala uses "move" which can result in unexpected content deletion.
  • Tint the active editor's boarder when dragging items over it, and show a file upload symbol over it.

• Fix attempting to extract svg dimensions from <svg viewData> attribute

• Fix error when rebuilding thumbnails ("Return value must be of the type string, null returned")