Provide credentials to relative links only

[rohankapoorcom]

Proposed change

In #6328, I added functionality to set cross-origin=use-credentials, to pass along credentials when loading Javascript Modules to work around some bugs in Safari.

@bramkragten noticed that this would be applied to requests that are actually going cross origin which was not the intent.

In this PR, I modified the code to check if the url is relative before setting cross-origin=use-credentials. If it's absolute i set it to cross-origin=anonymous, per @balloob's idea.

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New feature (thank you!)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Example configuration

None

Additional information

Checklist

• The code change is tested and works locally.
• There is no commented out code in this PR.
• Tests have been added to verify that the new code works.

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated for www.home-assistant.io