I want fail-over for resources

I want fail-over for resources such as scripts, CSS files, images, and so on. If a file is not available from one address, a backup source should be available. In particular this would be helpful for script files, where a sub-resource integrity failure could allow for failover to a different address for a copy of the file.

For example, if I'm using a script like jQuery from example.com and it changes (and so starts to fail sub-resource integrity checks), I want to be able to tell the browser to load the script file from another site. That way a change to a script on a CDN can't break my site.

The backup address may also support a different SRI hash.