Added DisplayActionSheetAsync to ShellNavigator#309

AndreasReitberger merged 2 commits intomainAndreasReitberger/SharedMauiCoreLibrary:mainfrom

308-add-displayactionsheetasync-to-shellnavigatorAndreasReitberger/SharedMauiCoreLibrary:308-add-displayactionsheetasync-to-shellnavigatorCopy head branch name to clipboard