add one-line intro

egs/librispeech/ASR/README.md

@@ -35,6 +35,7 @@ The following table lists the differences among them.
 | `lstm_transducer_stateless2`          | LSTM | Embedding + Conv1d | Using LSTM with mechanisms in reworked model + gigaspeech (multi-dataset setup) |
 | `lstm_transducer_stateless3`          | LSTM | Embedding + Conv1d | Using LSTM with mechanisms in reworked model + gradient filter + delay penalty |
 | `zipformer`                           | Upgraded Zipformer | Embedding + Conv1d | The latest recipe |
+| `zipformer_adapter`                           | Upgraded Zipformer | Embedding + Conv1d | It supports domain adaptation of Zipformer using parameter efficient adapters |
 
 The decoder in `transducer_stateless` is modified from the paper
 [Rnn-Transducer with Stateless Prediction Network](https://ieeexplore.ieee.org/document/9054419/).