feat: add macos CI (#1704)

PR adding macOS configuration to Example app and adding CI job for building the app on macOS.

Example/macos/Example-iOS/main.m

@@ -0,0 +1,9 @@
+#import <UIKit/UIKit.h>
+
+#import "AppDelegate.h"
+
+int main(int argc, char * argv[]) {
+  @autoreleasepool {
+    return UIApplicationMain(argc, argv, nil, NSStringFromClass([AppDelegate class]));
+  }
+}