add extension methods for SetAppTheme and SetAppThemeColor

[fredericoregateiro]

Description of Change

Linked Issues

• Fixes #
  [Proposal] Extension bindings for AppTheme and AppThemeColor #117

PR Checklist

• Has a linked Issue, and the Issue has been approved(bug) or Championed (feature/proposal)
• Has tests (if omitted, state reason in description)
• Has samples (if omitted, state reason in description)
• Rebased on top of main at time of PR
• Changes adhere to coding standard
• Documentation created or updated: Added app theme docs MicrosoftDocs/CommunityToolkit#157

Additional information

[brminnick]

Thanks @fredericoregateiro!

Your Proposal Champion is @bijington and he will help guide you through the New Feature Proposal Process.

The Proposal for this feature, #117, must first be approved by the core maintainer team before we can review, approve and merge this PR. Shaun will bring this feature to a vote at our upcoming Monthly Standup meeting this Thursday.

After it is approved, we'll also need you to write the Docs by opening a PR on our Docs repo: https://github.com/MicrosoftDocs/CommunityToolkit/

I did take a quick look at this PR and noticed a few things missing:

• Add Unit Tests
• Update the Sample App to display the use of the new feature.

Thanks again for your hard work!

[fredericoregateiro]

Thanks @brminnick
I'll be updating those taks as soon as i can

[bijington]

Thanks @brminnick
I'll be updating those taks as soon as i can

Thanks @fredericoregateiro, do let me know if you need any assistance with the tasks as I am here to assist in any way 👍

[jfversluis]

Docs are ready to go afaic

[brminnick]

This is looking really good!!!

I just have a concern about the method name, Style<T>.Add() because it is so similar to the existing Add that devs may accidentally use it + confuse for the existing API, not fully understanding that it is explicitly creating a new AppThemeBinding

[brminnick]

Approved!

Thanks so much @fredericoregateiro + @bijington!!!