Expose generation timings from server & update completions.js (#2116)
* use javascript generators as much cleaner API
Also add ways to access completion as promise and EventSource
* export llama_timings as struct and expose them in server
* update readme, update baked includes
* llama : uniform variable names + struct init
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Co-authored-by: Georgi Gerganov <ggerganov@gmail.com>