GitLab

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 😄 )

Co-authored-by: OlivierDehaene <23298448+OlivierDehaene@users.noreply.github.com>