Can we add the support for the Crypt facade to use custom encryption keys?

[apoorvpal01]

I realise that Illuminate\Encryption\Encrypter can be used with the custom encryption key, but could we have it either as an optional argument for Crypt::encrypt(mixed $value, bool $serialize = true, string $key = null) and then check if the $key is null, it could default to the config app key? I would be happy to send a PR for this if it feels like a useful change to the other developers...