SettingsViewController: Improve 3pid adding UI
SettingsViewController: Improve 3pid adding UI

- paint the “plus icon” in green when the 3pid input is editing.

vector-im/riot-ios,vector-im/vector-ios,vector-im/riot-ios,vector-im/vector-ios,vector-im/vector-ios,vector-im/riot-ios,vector-im/riot-ios,vector-im/riot-ios,vector-im/riot-ios