Integration with Existing Apps: Podfile example does not use `use_react_native!`, is incomplete

Description

React Native 0.60 added the Podfile macro use_react_native!. In 0.63, the macro was added to the template project Podfile, replacing tens of pod lines in the Podfile of a React Native iOS app. (See the change in upgrade-helper.)

However, the Integration with Existing Apps docs page still suggests adding all the pod lines manually. (Worse, it is out of date, missing some pods that the reader basically just has to figure out through trial and error.)

The documentation should just suggest using use_react_native!, like the template project does.

Documentation version

next, 0.67

Apri la pagina della documentazione «Integration with Existing Apps» e confronta il relativo esempio di Podfile con il Podfile del template React Native e con la modifica di upgrade-helper a cui si fa riferimento. Aggiorna l’esempio per consigliare l’uso di use_react_native! invece di righe pod manuali, quindi verifica che la documentazione successiva relativa alla versione 0.67 non richieda più ai lettori di dedurre i pod mancanti.