Update _release.md.erb
Update _release.md.erb

Add alpine 3.10 based GoCD agent image.
gocd/gocd.github.io,gocd/www.go.cd,gocd/www.go.cd,gocd/www.go.cd,gocd/gocd.github.io,GaneshSPatil/www.go.cd,gocd/gocd.github.io,gocd/www.go.cd,gocd/gocd.github.io,GaneshSPatil/www.go.cd,GaneshSPatil/www.go.cd,GaneshSPatil/www.go.cd