- Fix bug where animated stickers are not accepted by WhatsApp since v2.8.0
- It was noted that pywebp would collapse all frames.
- aed005b attempted to fix this by creating webp with variable frame duration.
- However, the webp created would not be accepted by WhatsApp.
- Solution: If there is duplicated frame, use Pillow to save WebP if available, or else use pywebp and display warning.
- Better compliance with wastickers format
- Fix compression success not shown if success on step 0