ci: add action workflow for ensuring minimum xcode version support #204

Job	Run time
Build Amplify Swift for iOS / Build Amplify-Package \| iOS	3m 21s
Build Amplify Swift for macOS / Build Amplify-Package \| macOS	3m 21s
Build Amplify Swift for tvOS / Build Amplify-Package \| tvOS	3m 8s
Build Amplify Swift for watchOS / Build Amplify-Package \| watchOS	3m 35s
Confirm Passing Build Steps	1s
	13m 26s

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