Add a 'Confirmed' screen when a DApp has staked SNT to rank

[andytudhope]

Currently, the only confirmation DApps who stake SNT to rank get is a slight change in the bubble at the top of the screen, which disappears quickly anyway (plus the DApp appearing immediately in the 'Highest Ranked' section, though not necessarily in the visible part of it, esp on mobile screens).

It would be nice to add a proper "Confirmed! 🎉" screen when the tx is successful. However, we'll need a good design first, so this issue is just a placeholder for now.