feat: Adding themeService

[nickrandolph]

PR Type

What kind of change does this PR introduce?

• Feature

What is the current behavior?

Have to manually add reference to uno.extensions.core.winui

What is the new behavior?

REference to uno.extensions.core.winui is already added to the project

PR Checklist

Please check if your PR fulfills the following requirements:

• Tested code with current supported SDKs
• Docs have been added/updated which fit documentation template. (for bug fixes / features)
• Unit Tests and/or UI Tests for the changes have been added (for bug fixes / features) (if applicable)
• Wasm UI Tests are not showing unexpected any differences. Validate PR Screenshots Compare Test Run results.
• Contains NO breaking changes
• Updated the Release Notes
• Associated with an issue (GitHub or internal)

Other information

Internal Issue (If applicable):

[Youssef1313]

LGTM, but this only adds some PackageReferences. What APIs should be used from this package? Could there be some C# code added to the template showing how to do it? (even if the code is commented out)

[nickrandolph]

There will be but for now we need the package references for simplecalc