feature: embedded webview for non-mobile logins

[metalurgical]

Currently the login will open in the default external browser for non-mobile logins (mac, linux, windows), however no window focus switching will take place.

It would be better to implement an embedded webview if possible similar to what is done with mobile. This is due to a user in fullscreen or window-fullscreen mode not seeing the browser open and it will not be obvious that they would need to alt-tab (or equivalent) to get to the login screen.

Here is a starting point:
https://docs.unrealengine.com/5.3/en-US/API/Runtime/WebBrowser/