docs(issue-10): fix usage long description in completion

Author: davidebianchi

README.md

@@ -111,6 +111,7 @@ Completion could be generate running the `miactl completion zsh` command
 
 The generated completion script should be put somewhere in your $fpath named _miactl.
 
+
 [github-actions]: https://github.com/mia-platform/miactl/actions
 [github-actions-svg]: https://github.com/mia-platform/miactl/workflows/Test%20and%20build/badge.svg
 [godoc-svg]: https://godoc.org/github.com/mia-platform/miactl?status.svg

cmd/completion.go

@@ -20,9 +20,10 @@ func newCompletionCmd(rootCmd *cobra.Command) *cobra.Command {
 
 	miactl completion fish >~/.config/fish/completions/miactl.fish
 
-	For zsh, add the following to your ~/.zshrc file:
+	For zsh:
 
-	source <(miactl completion zsh)
+	To generate the completion script, run miactl completion zsh
+	the generated completion script should be put somewhere in your $fpath named _miactl
 
 	---