貌似不能支持webp 动图的？

**Describe the bug**
A clear and concise description of what the bug is.

**To Reproduce**
Steps to reproduce the behavior:
1. Go to '...'
2. Click on '....'
3. Scroll down to '....'
4. See error

**Expected behavior**
A clear and concise description of what you expected to happen.

**Screenshots**
If applicable, add screenshots to help explain your problem.

**Versions (please complete the following information):**
- Device: [e.g. iPhone6]
- OS: [e.g. iOS8.1]
- `flutter doctor -v`:
- power_image Version: [e.g. 0.1.0]
- power_image_ext Version: [e.g. 2.5.3]

**Additional context**
Add any other context about the problem here.

Start by reproducing the reported animated WebP behavior in the Flutter plugin and record the device, OS, Flutter doctor output, and power_image and power_image_ext versions. Compare the result with the expected animated WebP display; the issue is done when the supported behavior is confirmed or the missing support is documented with a focused reproduction.

Written by the indexing model from the issue text.