backplateImgUrl does not adjust to fit to the canvas when zoom in/zoom out

[hoan-anh]

Describe the bug
backplateImgUrl does not adjust to fit to the canvas when zoom in/zoom out, its size stays the same.

Painterro version
v1.2.87

To Reproduce
Steps to reproduce the behavior:

1. Initiate Painterro with the backplateImgUrl parameter:
   Painterro({
   backplateImgUrl: 'image-url'
   }).show()

2. Use Ctrl + scroll to zoom in/out of the canvas

Expected behavior
The backplate img should also zoom in/out to fit with the canvas

Screenshots
Before zooming:

After zooming in:

Browser
Google Chrome 133 on Windows 11