[Feature request] Hide secret keys in the UI but with button to display them

[gelavat]

It would be good to hide the secret key in the edit of a TOTP, with asterisks, so that hackers are not able to do a screen capture to steal it, when we edit it. This would add some security to the system.

However a button to the right of this secret key would be shown and clicking it would display the secret key so that we can quickly backup it.