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![image](https://github.com/huggingface/text-generation-inference/assets/3841370/58177321-479f-4ad1-b3bc-cec027423984)

Closes #478

This PR starts the minimal possible amount of explanation I could think
of. It tries to explain how dynamic batching occurs, the interactions
with past key values and ignores the padding problem.

Maybe some drawings could help too but I kept it to text for now.

OPT models do not all have a `tokenizer.json` file on the hub at the
moment. Can't merge for now.

Co-authored-by: OlivierDehaene <olivier@huggingface.co>

https://en.wikipedia.org/wiki/Server-sent_events

Adds some bits for first-time users (like me 😄 )