Suggestion: Add feedback button

[bjornwgnr]

Add feedback button that either links to https://github.com/paritytech/fether/issues/new or automatically creates a GH issue from whatever is put in a short form?

(there are probably more sophisticated methods to achieve this)

[Tbaut]

as we don't want to encourage users to use the app on an online device!

That's not the signer, users should be online. A feedback button is a good idea.