[CLAP] Add CLAP to the library
# What does this PR do?
Adds CLAP to the HF library cc @younesbelkada
Now we should create a new task : `zero-shot audio classification`! 
<|||||>_The documentation is not available anymore as the PR was closed or merged._<|||||>Ok! Looking very good, last thing is the `configuration` docstring. @younesbelkada will finish this 😉 <|||||>Models are here (with nice model cards hehe):
- https://huggingface.co/ybelkada/clap-htsat-fused
- https://huggingface.co/ybelkada/clap-htsat-unfused
Will transfer them on `laion-ai` once we got an approval :)<|||||>1. Some renaming has to happen to normalise the parameters around mel extraction. Will do this and everything should look good 😉 
2. Add the dependency on torchvision as the np implementation received a big NO 😢 <|||||>Found a few discrepancies with the various variables in the config that are not used. Will finish asap should makes things clearer. <|||||>Ok I broke the history 
