Indicate sign/transaction request from URL

[hesterbruikman]

Problem

Currently there is no distinction between message sign/transaction requests triggered by a dapp, wallet or URL. In case of a URL request the user might want to verify that, and what, website triggered the request

User story

As a user
I wanted to be made aware that a sign/transaction request was triggered by a URI (i.e. eip-681),
because it helps me verify content of the request

Notes

This could be a redirect/interstitial when opening a deep link or an indicator on the sign screen. Note that on Mobile, there is not immediate sign request, rather a pre-filled transaction builder. This might not work for message sign requests (cc @jrainville)