Change 2FA code lifetime

[onamanzi]

Hello
I started working with fortify and noticed that the code generated by the Google authenticator or another can be used multiple times in 1 minute even though the 2FA application generates a new one every 30 seconds.

Investigating a bit in the documentation of pragmarx/google2fa I've managed to change the code lifetime to 30 seconds through the window property, using $this->engine->setWindow(0); directly in the function verify in vendor/laravel/fortify/src/TwoFactorAuthenticationProvider.php.

I've not been able to find information in the laravel documentation to help me modify the duration of the code from a provider configuration file, I am not sure how practical it is to implement something like this but it would be helpful to change the duration of the 2FA code.

[driesvints]

Would probably need to be provided as a config option up front through a closure based instantiation here: https://github.com/laravel/fortify/blob/1.x/src/FortifyServiceProvider.php#L50

I think this is a valid suggestion. Welcoming PR's.