fix: bundle CSS is not injected properly

[OEvgeny]

Fixes #

Changelog Entry

• The botframework-webchat package now uses CSS modules for styling purposes, in PR #5666, in PR #5677 by @OEvgeny

Description

Hotfix for my previous changes so NPM built Web Chat has the styles as well.

Specific Changes

• I have added tests and executed them locally
• I have updated CHANGELOG.md
• I have updated documentation

Review Checklist

This section is for contributors to review your work.

• Accessibility reviewed (tab order, content readability, alt text, color contrast)
• Browser and platform compatibilities reviewed
• CSS styles reviewed (minimal rules, no z-index)
• Documents reviewed (docs, samples, live demo)
• Internationalization reviewed (strings, unit formatting)
• package.json and package-lock.json reviewed
• Security reviewed (no data URIs, check for nonce leak)
• Tests reviewed (coverage, legitimacy)