Add initial support for Multiple Windows on MacOS

[ne0rrmatrix]

• Bug fix

Description of Change

Add support for more than one window on MacOS. With this PR Media Element will now show multiple windows when you visit the Multi-Window Page on MacOS.

Linked Issues

• Fixes [BUG] MediaElement not supported in a DataTemplate on MacCatalyst in an application using multiple windows  #2249

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: Update MacOS instructions for Plist manifest MicrosoftDocs/CommunityToolkit#476

Additional information

With this PR MacOS will fully support multiple windows on MacOS when using Media Element. Documentation will need updating to add the changes to Manifest file for MacOS.

[brminnick]

Nice! Could you open a Docs PR to add this info to the MediaElement Platform Specific Initialization section before we merge this PR?

https://learn.microsoft.com/en-us/dotnet/communitytoolkit/maui/views/mediaelement?tabs=mac#platform-specific-initialization

[ne0rrmatrix]

Nice! Could you open a Docs PR to add this info to the MediaElement Platform Specific Initialization section before we merge this PR?

https://learn.microsoft.com/en-us/dotnet/communitytoolkit/maui/views/mediaelement?tabs=mac#platform-specific-initialization

Yes I will do that now 😄