Show details about action when user lands on login page through a URI link

[irisli]

If user clicked on a URI link, let them know they will be taken to that action after they log in.

For example, open this link in incognito window (or new session): https://launch.stellar.org/#/?action=send&dest=stellartalk.org&amount=800&currency=STR

It'll prepopulate the send field after you log in but you won't know that until you actually log in.

[wynlim]

let me think about how to communicate this in the UI