Bug report

• I've updated both my project and my packages to the latest Frontity versions: https://docs.frontity.org/guides/keep-frontity-updated
• I've searched for existing issues.
• I've checked the documentation: https://docs.frontity.org
• I've checked the community forum: https://community.frontity.org

Expected behavior
Correctly styled rendering on the server side without any warnings when you add a static url from the server assets to the css props (like a background image)

Observed behavior
If you import an image and you add it as a background-image via css or style props, the console shows a warning,

Screenshots

Steps involved to reproduce the problem

1. Create a frontity repository: npx frontity create
2. Add any image the theme package
3. Import it on the component index
4. Add it as a background of any html element

I have created a repository with a hyper-simplified version of frontity where there is only a div with a static image as background: https://github.com/husseincak/testing/

Info about the problem
If you downgrade the package @frontity/core to the v 1.14.3, the warning no longer appears:

• @frontity/core: ^1.15.1 => 1.14.3
  If i console.log the asset i get two different urls on the client and on the server:
• Background URL on client: /static/images/image.jpg
• Background URL on the server: __webpack_public_path__images/image.jpg

Maybe the problem is because the two urls are diferent so the component is being rendered as a different component on the server and on the client