Simple helper for use SafeAreaLayoutGuide if available

[portellaa]

Since now we have a new safe area layout guide, it can get messy if we need to use it when compiling for iOS versions prior to 11.

This is a small helper to make it cleaner when you need to use SafeAreaLayoutGuide.

[orta]

Cool, sure, there's no documentation in the README for this - which it probably needs, but I'm gonna ship it anyway. Would love to see that later 👍

[portellaa]

Cool, i will do it in the meanwhile 😉 thanks 🙏 🚀