Update documentation for first time users

[sumur1au]

First of all, thank you so much for your hard work with the integration; this has saved me from mucking around with ESPHome devices.

For those who have purchased new units with the built-in WiFi module, you can avoid downloading the Mitsubishi Wi-Fi application and setting up a user account altogether.

Steps:

1. Scan the QR code to join the unit’s WiFi network.
2. Open a web browser and go to http://192.168.11.1/network.
3. Choose your home WiFi network from the list and connect by entering the password.
4. Follow the on-screen steps to complete the integration setup.