Documentation missing for canGoBack()

Current Behavior

According to @satya164 in react-navigation/react-navigation#7814 we should use canGoBack() to guard against going back too much. If we don't, it'll result in a console.error() being emitted (red screen).

canGoBack is an undocumented feature. It's only mentioned in passing in the 'upgrading from 3.x' article where it's mentioned as a feature on the HeaderBackButton, however the function is (also?) available on the navigator object.

Expected Behavior
Typing "canGoBack" in search field in the documentation should yield this result.

How to reproduce

1. Open https://reactnavigation.org/docs
2. Type "canGoBack" in upper right search field

** Other comments **

It may make sense to reference the new documentation for canGoBack() in relation to goBack(), pop(), jumpTo(), and popToTop().

Comienza buscando en la documentación las referencias existentes a canGoBack(), goBack(), pop(), jumpTo() y popToTop(). Añade una entrada de canGoBack() que se pueda encontrar mediante búsqueda y que explique su disponibilidad y su propósito como protección, con enlaces a los métodos de navegación relacionados; se considera terminado cuando buscar canGoBack en la documentación devuelve la nueva explicación.