Provide pairing code as option to login

[carefulcomputer]

Currently the api returns the QR code to login. Can you please also provide a way to login using code (https://docs.wwebjs.dev/Client.html#requestPairingCode)

[avoylenko]

@carefulcomputer i have implemented the method in a forked project https://github.com/avoylenko/wwebjs-api. Feel free to switch until @chrishubert is implemented the route here.