TV: maybe mention direct back needed for deep link activation

[birbilis]

https://github.com/DelphiWorlds/HowTo/tree/main/Demos/TV

mentions FPreventExit being used so that back doesn't exit

maybe this is also useful to be mentioned regarding having activated app via deep link (where one needs to immediately exit): https://developer.android.com/training/tv/get-started/navigation#direct-back