Add links to training recipes (#2812)

Summary:
<img width="756" alt="Screen Shot 2022-11-01 at 3 32 58 PM" src="https://user-images.githubusercontent.com/855818/199173348-f463ae71-438c-4dad-a481-b65522a8e52f.png">

Pull Request resolved: https://github.com/pytorch/audio/pull/2812

Reviewed By: carolineechen

Differential Revision: D40919942

Pulled By: mthrok

fbshipit-source-id: 18e5a709c262fb0b15ada0d303f1d0dee033beb1

docs/source/_templates/layout.html

@@ -55,7 +55,7 @@
 
 {%- block footer %}
     <script type="text/javascript">
-    var collapsedSections = ['API Tutorials', 'Pipeline Tutorials']
+    var collapsedSections = ['API Tutorials', 'Pipeline Tutorials', 'Training Recipes']
     </script>
     {{ super() }}
     <script type="text/javascript">

docs/source/index.rst

@@ -52,6 +52,16 @@ model implementations and application components.
    tutorials/mvdr_tutorial
    tutorials/hybrid_demucs_tutorial
 
+.. toctree::
+   :maxdepth: 1
+   :caption: Training Recipes
+   :hidden:
+
+   Conformer RNN-T ASR <https://github.com/pytorch/audio/tree/main/examples/asr/librispeech_conformer_rnnt>
+   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>
+
 .. toctree::
    :maxdepth: 1
    :caption: API Reference