FR: Add option for manual offset

[JasonTheAdams]

Describe the bug
We have an iframe with a box shadow. When the iframe resizes the box shadow is clipped as it's not calculated in the container height.

To Reproduce
Steps to reproduce the behavior:

1. Create an iframe with a box shadow
2. Resize the iframe to a new height
3. Look at the bottom of the iframe and notice the box shadow is clipped

Expected behavior
If there was an offsetHeight option, we could simply set a value which compensates for the box shadow. The offset would simply be applied to the final calculated height and would be a constant. It wouldn't be necessary for us, but allowing for a callback could also be helpful for someone to calculate the offset at each moment of resize.

Screenshots

Desktop (please complete the following information):

• OS: MacOS
• Browser Brave
• Version 1.34.80

[davidjbradshaw]

Happy to take a PR for this, can you please add width as well

[davidjbradshaw]

Fixed in V5.0.0 #1205