[DOCS] add -i flag to curl HEAD call

without -i you never see the status:200 or status:404 messages

docs/reference/indices/types-exists.asciidoc

@@ -5,7 +5,7 @@ Used to check if a type/types exists in an index/indices.
 
 [source,js]
 --------------------------------------------------
-curl -XHEAD 'http://localhost:9200/twitter/tweet'
+curl -XHEAD -i 'http://localhost:9200/twitter/tweet'
 --------------------------------------------------
 
 The HTTP status code indicates if the type exists or not. A `404` means