Invoice Noscript UI Extension Point

[rafael-xmr]

The ability to inject an <iframe /> or a simple link url into the invoice-noscript page so that a plugin for coin swaps for example can still be enabled for customers even when they are browsing without javascript. trocador.app is built by scratch without javascript for example so it would work fine for those users.

[dennisreimann]

Thanks, I've added a PR for this: #4532