Add browser iframe host to config

[DanielaMazur]

This pull request reallocates the browser iframe host into the configuration. Currently, the host is hardcoded, making any attempt to modify the domain impossible. The necessity for such flexibility arises when, for instance, encountering firewall restrictions that impede the default domain.

By incorporating this domain into the configuration, developers gain the ability to customize it, facilitating scenarios where the default domain faces access challenges. This modification proves especially valuable when a custom domain is employed to act as a proxy, redirecting requests to apis.google.com.

[changeset-bot[bot]]

🦋 Changeset detected

Latest commit: 427d037756615548da3c477aa2387c07d05cea3b

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 3 packages

Name	Type
@firebase/auth	Patch
@firebase/auth-compat	Patch
firebase	Patch

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