feat: pretty-print JSON output (#610)

This PR makes the JSON output (for example when using `... describe
-o=json`) properly formatted, with 2 spaces as indent.

internal/cmd/util/util.go

@@ -158,6 +158,7 @@ func DescribeFormat(object interface{}, format string) error {
 
 func DescribeJSON(object interface{}) error {
 	enc := json.NewEncoder(os.Stdout)
+	enc.SetIndent("", "  ")
 	return enc.Encode(object)
 }