whisper -> wav2vec2 conversion

[rroohhh]

For alignment we use wav2vec2, with a character level alphabet. The transcript generated by whisper has to be converted into a transcript using only the characters know to the wav2vec2 model to perform alignment.

The currently conversion performed by the worker for this is very unsophisticated.

1. First every space is replace with |, which is the token used by wav2vec2 as a word separator
2. Any character not present in the wav2vec2 alphabet is simply dropped.

There are several improvements to this:

1. Use something like unicode normalization (for example NFKD) to try to replace characters in the whisper transcript, that are not present in the wav2vec2 with ones that could be present.
2. Handle languages with no word separators (chinese, japanese, etc)
3. Add handling for punctuation (. is also a word separator. What about words joined using a -?)