Time stamps for CTC models (#15687)

* [Wav2Vec2 Time Stamps]

* Add first version

* add word time stamps

* Fix

* save intermediate space

* improve

* [Finish CTC Tokenizer]

* remove @

* remove @

* push

* continue with phonemes

* up

* finish PR

* up

* add example

* rename

* finish

* Apply suggestions from code review

Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>

* correct split

* finalize

Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>

docs/source/model_doc/wav2vec2.mdx

@@ -45,6 +45,8 @@ This model was contributed by [patrickvonplaten](https://huggingface.co/patrickv
 [[autodoc]] Wav2Vec2CTCTokenizer
     - __call__
     - save_vocabulary
+    - decode
+    - batch_decode
 
 ## Wav2Vec2FeatureExtractor