Improving first-use user experience

[jupjohn]

The first-use experience for new users is relatively poor. I'd like to take ideas in this discussion as to what could be changed/improved.

What users see when they first open the app:

[jupjohn]

Alongside the "click to add a split" label, showing a "login with Twitch" button would instantly prompt the user to login instead of having to find where to add accounts.

[Nerixyz]

See also #4273.