Add Wi-Fi setup to settings

[rock3r]

The settings screen should display a "configure conference Wi-Fi" item if the device runs iOS 11+ and the app has Wifi configuration data. If the hotspot is already configured on the device, it should be marked as "already done".

⚠️ There is still no designs for this story

⚠️ Blocked by #48 (implementing the WiFi setup code)

🗒 Wi-Fi setup is only available on iOS 11+

🗒 This setting can only be shown if the app has the WiFi configuration data, otherwise it must be hidden.