Add a `gofumports` as a new linter

[SVilgelm]

gofumpt also has gofumports. Any way we can sneak that in here?

Originally posted by @andrewrynhard in #1239 (comment)

[boring-cyborg]

Hey, thank you for opening your first Issue ! 🙂 If you would like to contribute we have a guide for contributors.

[dnwe]

@SVilgelm see mvdan/gofumpt#75

There isn’t really a need for gofumports in golangci-lint

[SVilgelm]

@dnwe thank you, so we can close this issue