fix: Allows legacy ref to css exports

[Azayzel]

Description:

This PR allows users to upgrade to the latest version without experiencing css export path issues. My team and I had went from "@okta/okta-signin-widget": "6.9.0", -> "@okta/okta-signin-widget": "7.3.1", and experienced this css path issue.

PR Checklist

• Have you verified the basic functionality for this change?
• Did you add tests, as appropriate, following our Automated Test guidelines?
• Did you follow our Security Best Practices?
• Did you verify the change by running downstream monolith artifact? (Provide link to build below)
• Does this PR include noticeable changes to the UI? (If yes, attach screenshots/video below)

Issue:

• No current Issue to reference

Reviewers:

Screenshot/Video:

Before the Change, a user would see the below error

IME, the error would manifest itself when referencing the legacy path from a *.css file

SO
To fix user from potentially breaking when upgrading, i recommend the below change to allow for the legacy reference path to be covered as well. Maybe this could be better explained or referenced in the Migration Guide

Downstream Monolith Build: