gitignore: add newline to `gi` output (#7586)

* Add trailing new line at the end of output
* Double-quote variable expansion

plugins/gitignore/gitignore.plugin.zsh

-function gi() { curl -fL https://www.gitignore.io/api/${(j:,:)@} }
+function gi() { curl -fLw '\n' https://www.gitignore.io/api/"${(j:,:)@}" }
 
 _gitignoreio_get_command_list() {
   curl -sfL https://www.gitignore.io/api/list | tr "," "\n"