feat: make shadow root adopt scoped component styles

[tomherni]

Prerequisites

• I have read the Contributing Guidelines.
• I agree to follow the Code of Conduct.
• I have searched for existing issues that already include this feature request, without success.

Describe the Feature Request

When a scoped component is inside a shadow root, rather than adding the component styles to a <style> tag, add them to the shadow root's adopted stylesheets.

Describe the Use Case

This is an improvement for browsers that support adopting stylesheets, which would be the majority of users nowadays.

Additional Information

It wasn't much effort, so I just went ahead and created a pull request #6028. Feedback is much appreciated.