[Whisper] Add conversion script for the tokenizer (#27338)

* draft

* updates

* full conversion taken from `https://gist.github.com/xenova/a452a6474428de0182b17605a98631ee`

* psuh

* nits

* updates

* more nits

* Add co author

Co-authored-by: Joshua Lochner <admin@xenova.com>

* fixup

* cleanup

* styling

* add proper path

* update

* nits

* don't  push the exit

* clean

* update whisper doc

* don't error out if tiktoken is not here

* make sure we are BC with conversion

* nit

* Update docs/source/en/model_doc/whisper.md

Co-authored-by: amyeroberts <22614925+amyeroberts@users.noreply.github.com>

* merge and update

* update markdwon

* Co-authored-by: Sanchit Gandhi <93869735+sanchit-gandhi@users.noreply.github.com>

---------

Co-authored-by: Joshua Lochner <admin@xenova.com>
Co-authored-by: amyeroberts <22614925+amyeroberts@users.noreply.github.com>

docs/source/en/model_doc/whisper.md

@@ -34,8 +34,13 @@ The original code can be found [here](https://github.com/openai/whisper).
 - Inference is currently only implemented for short-form i.e. audio is pre-segmented into <=30s segments. Long-form (including timestamps) will be implemented in a future release.
 - One can use [`WhisperProcessor`] to prepare audio for the model, and decode the predicted ID's back into text.
 
-This model was contributed by [Arthur Zucker](https://huggingface.co/ArthurZ). The Tensorflow version of this model was contributed by [amyeroberts](https://huggingface.co/amyeroberts).
-The original code can be found [here](https://github.com/openai/whisper).
+- To convert the tokenizer, we recommend using the following:
+
+```bash
+python src/transformers/models/whisper/convert_openai_to_hf.py --checkpoint_path "" --pytorch_dump_folder_path "Arthur/whisper-3" --convert_tokenizer True --whisper_version 3 --multilingual True
+```
+Here the `whisper_version` will set the number of languages to `100` to account for `cantonese` which was added in `whisper-large-v3`.
+
 
 ## Inference