Add completion step for brew

Author: sayboras

.goreleaser.yml

@@ -92,6 +92,8 @@ brews:
       (bash_completion/"golangci-lint").write output
       output = Utils.popen_read("#{bin}/golangci-lint completion zsh")
       (zsh_completion/"_golangci-lint").write output
+      output = Utils.popen_read("#{bin}/golangci-lint completion fish")
+      (fish_completion/"eksctl.fish").write output
       prefix.install_metafiles
     test: |
       system "#{bin}/golangci-lint --version"