Support of PGP signed commits and tags

[Cysioland]

Just showing, who signed them will be great

[scriptbae]

+1. Would be awesome to have this in Gogs now that it's been deployed as a GitHub feature!

[ikaros]

+1

Agree that this should be a thing.

[tuxxy]

I would very much so enjoy this feature, as well!

[bkcsoft]

I'm claiming this :)

[Fastidious]

I am adding my "voice" to this request. I love Gogs!

[Jitsusama]

I would love this too!