whisper : add grammar-based sampling (#1229)
* whisper : add grammar-based sampling
* build : fix after master merge
* command : fix exception when recognizing the command
* whisper : fine-tuning grammar functionality
* command : grammar-related improvements
- option to read grammar from file
- add sample grammars for colors and chess moves
- fine-tune the performance further
* grammars : add assistant + update comments
* command : enable beam-search, add "no_timestamps", add "context", add p
* whisper : remove comment
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Co-authored-by: Georgi Gerganov <ggerganov@gmail.com>
