include a link to index.rst (#3441)

Summary:
Include Conformer/Emformer RNN-T ASR/VSR/AV-ASR link to index.rst

Pull Request resolved: https://github.com/pytorch/audio/pull/3441

Differential Revision: D47094158

Pulled By: mthrok

fbshipit-source-id: 9ab42ac2bf52a5ce488003897ffba2f10a6ca941

docs/source/index.rst

@@ -85,6 +85,7 @@ model implementations and application components.
    Emformer RNN-T ASR <https://github.com/pytorch/audio/tree/main/examples/asr/emformer_rnnt>
    Conv-TasNet Source Separation <https://github.com/pytorch/audio/tree/main/examples/source_separation>
    HuBERT Pre-training and Fine-tuning (ASR) <https://github.com/pytorch/audio/tree/main/examples/hubert>
+   Conformer/Emformer RNN-T ASR/VSR/AV-ASR <https://github.com/pytorch/audio/tree/main/examples/asr/avsr_rnnt>
 
 .. toctree::
    :maxdepth: 1