Add net6.0-maccatalyst support

[aritchie]

✨ What kind of change does this PR introduce? (Bug fix, feature, docs update...)

This adds net6.0-maccatalyst support as well as adding a new MAUI app that targets iOS and Catalyst
To support catalyst, only one method needed to be compiler flagged:
private float GetKeyboardHeightFromNotification(NSNotification? notification, bool ignoreOrientation,
UIInterfaceOrientation orientation, ref double animationDuration) => 0;

⤵️ What is the current behavior?

N/A

🆕 What is the new behavior (if this is a feature change)?

N/A

💥 Does this PR introduce a breaking change?

No

🐛 Recommendations for testing

Same as iOS

📝 Links to relevant issues/docs

#98

🤔 Checklist before submitting

• All projects build
• Follows style guide lines
• Relevant documentation was updated

[Cheesebaron]

Cool! Seems to work nice.

For someone who wants to try, make sure to do:

dotnet workload install ios maccatalyst

Then you can build and run with:

dotnet build -t:Build -p:Configuration=Debug -f net6.0-maccatalyst BTProgressHUDDemo2/BTProgressHUDDemo2.csproj
dotnet build -t:Run -p:Configuration=Debug -f net6.0-maccatalyst BTProgressHUDDemo2/BTProgressHUDDemo2.csproj