Introduced features

• Updated underyling libhief library

Introduced features

• Library is now fully async, non-blocking, and utilizes web workers
• Animated heic files are converted to animated gif files
• Support for multiple output (outputting multiple images out of a heic continaer)
• Detects if file is already a browser-consumable image

Bug fixes

• #9 "Cannot assign to read only property..."
• #8 support for more variations of heic files