[audio] add CTC forced alignment API tutorial to torchaudio (#3356)

Summary:
Pull Request resolved: https://github.com/pytorch/audio/pull/3356

move the forced aligner tutorial to torchaudio, with some formatting changes

Reviewed By: mthrok

Differential Revision: D46060238

fbshipit-source-id: d90e7db5669a58d1e9ef5c2ec3c6d175b4e394ec

docs/source/index.rst

@@ -67,6 +67,7 @@ model implementations and application components.
    tutorials/asr_inference_with_ctc_decoder_tutorial
    tutorials/online_asr_tutorial
    tutorials/device_asr
+   tutorials/ctc_forced_alignment_api_tutorial
    tutorials/forced_alignment_tutorial
    tutorials/tacotron2_pipeline_tutorial
    tutorials/mvdr_tutorial
@@ -148,6 +149,13 @@ Tutorials
    :link: tutorials/audio_io_tutorial.html
    :tags: I/O
 
+.. customcarditem::
+   :header: CTC Forced Alignment API
+   :card_description: Learn how to use TorchAudio's CTC forced alignment API (<code>torchaudio.functional.forced_align</code>).
+   :image: https://download.pytorch.org/torchaudio/tutorial-assets/thumbnails/ctc_forced_alignment_api_tutorial.png
+   :link: tutorials/ctc_forced_alignment_api_tutorial.html
+   :tags: CTC,Forced-Alignment
+
 .. customcarditem::
    :header: Streaming media decoding with StreamReader
    :card_description: Learn how to load audio/video to Tensors using <code>torchaudio.io.StreamReader</code> class.