docs(faq): explained workaround when browser gets killed when going to background

[mateoguzmana]

Changes

Adding full documented workaround to fix the issue when the Auth0 browser gets killed when going to the background and re-launching. It is an adjusted version of the solution for the Stripe SDK.

This seems to be a common issue that has been mentioned several times and a proper workaround in the docs could save a lot of time for new people discovering this issue as it is not that clear why it happens.

References

• Android: OTP auth browser closes when minimising app
• Fixed authentication restart when the app is minimized
• possibility to run with launchMode:singleTop?
• Android singleTask launch mode is required for react-native deep links

Testing

• [x] This change has been tested on the latest version of the platform/language or why not

Checklist

• [x] I have read the Auth0 general contribution guidelines
• [x] All existing and new tests complete without errors
• [x] All active GitHub checks have passed