Update readme

PiperOrigin-RevId: 447111360

official/README.md

@@ -66,12 +66,32 @@ In the near future, we will add:
 
 ### [Natural Language Processing](nlp/README.md)
 
+#### Pre-trained Language Model
+
+| Model | Reference (Paper) |
+|-------|-------------------|
+| [ALBERT](nlp/MODEL_GARDEN.md#available-model-configs) | [ALBERT: A Lite BERT for Self-supervised Learning of Language Representations](https://arxiv.org/abs/1909.11942) |
+| [BERT](nlp/MODEL_GARDEN.md#available-model-configs) | [BERT: Pre-training of Deep Bidirectional Transformers for Language Understanding](https://arxiv.org/abs/1810.04805) |
+| [ELECTRA](nlp/tasks/electra_task.py) | [ELECTRA: Pre-training Text Encoders as Discriminators Rather Than Generators](https://arxiv.org/abs/2003.10555) |
+
+
+#### Neural Machine Translation
+
 | Model | Reference (Paper) |
 |-------|-------------------|
-| [ALBERT (A Lite BERT)](nlp/MODEL_GARDEN.md#available-model-configs) | [ALBERT: A Lite BERT for Self-supervised Learning of Language Representations](https://arxiv.org/abs/1909.11942) |
-| [BERT (Bidirectional Encoder Representations from Transformers)](nlp/MODEL_GARDEN.md#available-model-configs) | [BERT: Pre-training of Deep Bidirectional Transformers for Language Understanding](https://arxiv.org/abs/1810.04805) |
-| [NHNet (News Headline generation model)](projects/nhnet) | [Generating Representative Headlines for News Stories](https://arxiv.org/abs/2001.09386) |
 | [Transformer](nlp/MODEL_GARDEN.md#available-model-configs) | [Attention Is All You Need](https://arxiv.org/abs/1706.03762) |
+
+#### Natural Language Generation
+
+| Model | Reference (Paper) |
+|-------|-------------------|
+| [NHNet (News Headline generation model)](projects/nhnet) | [Generating Representative Headlines for News Stories](https://arxiv.org/abs/2001.09386) |
+
+
+#### Knowledge Distillation
+
+| Model | Reference (Paper) |
+|-------|-------------------|
 | [MobileBERT](projects/mobilebert) | [MobileBERT: a Compact Task-Agnostic BERT for Resource-Limited Devices](https://arxiv.org/abs/2004.02984) |
 
 ### Recommendation