Use atotto/clipboard fork

**Is your feature request related to a problem? Please describe.**
https://github.com/atotto/clipboard was unmaintained during 4 years and have not merged these useful request like https://github.com/atotto/clipboard/pull/64

There is a [fork](https://github.com/gopasspw/clipboard) initied by the devs of https://github.com/gopasspw/gopass I think it would be nice to move to this as clipboard stuff is really sensible. At the first look I don't see breaking change implemented.