Option for opening signer provider in popup instead of iframe

[WavescapTorben]

Heyho) Maybe you could provide an option so that the signer provider could be shown in a popup (window.open()) instead of showing it in an iframe. I think this could increase trust into the tool, because with the current iframe solution, it is possible to overlap the signer iframe by a <div style="position:fixed;z-index:9999999999999999999;[...]"></div> element and for example show an other amount and recipient of the transaction a user is signing. Sure, if a website owner would do such a thing, he would quickly lose all his users, but his website could also have been hacked..