Add XML comments to reduce CS1591 warnings

[9rnsr]

Separate PR from #781

[michael-hawker]

Sorry for delay here, thanks so much!

[michael-hawker]

@Arlodotexe have you seen this type of message before on the UWP build?

       "D:\a\Labs-Windows\Labs-Windows\CommunityToolkit.AllComponents.sln" (default target) (1:2) ->
       "D:\a\Labs-Windows\Labs-Windows\tooling\ProjectHeads\AllComponents\Uwp\CommunityToolkit.App.Uwp.csproj" (default target) (45:6) ->
       (BuildNativePackage target) -> 
         C:\Program Files (x86)\Microsoft SDKs\UWPNuGetPackages\microsoft.net.native.compiler\2.2.12-rel-31116-00\tools\Microsoft.NetNative.targets(809,5): error : Internal compiler error: Failed to parse 'S' [D:\a\Labs-Windows\Labs-Windows\tooling\ProjectHeads\AllComponents\Uwp\CommunityToolkit.App.Uwp.csproj]