Add "json" as output type (#513)

Co-authored-by: Norwin <git@nroo.de>
Reviewed-on: https://gitea.com/gitea/tea/pulls/513
Reviewed-by: Norwin <noerw@noreply.gitea.io>
Reviewed-by: strk <strk@noreply.gitea.io>

cmd/flags/generic.go

@@ -33,7 +33,7 @@ var RemoteFlag = cli.StringFlag{
 var OutputFlag = cli.StringFlag{
 	Name:    "output",
 	Aliases: []string{"o"},
-	Usage:   "Output format. (csv, simple, table, tsv, yaml)",
+	Usage:   "Output format. (simple, table, csv, tsv, yaml, json)",
 }
 
 // PaginationPageFlag provides flag for pagination options