Offer a way to just login without using XMPP

[Luc1412]

Reason:

Save memory and bandwidth when using fortnitepy to just fetch some data.

Implementation:

Similar to Discord.py a connect() and login() method can be useful. Connect connects to XMPP, Login just handles authorization.

.start() and .run() will execute both.

[Terbau]

I was originally against this as it seemed too complicated and would only further confuse users of the library, but after thinking about it for some time I arrived at a solution I feel fits this library. Instead of having to mess around with methods, you can choose to use either BasicClient or Client.

I have only tested that basic functionality works in both. I'm yet to test all methods, but since I might be gone for a few days I decided to push the commit so others can test it if they want. I will also get around to creating an example for the usage of this new client.

I will leave this issue open until both clients have been tested properly.