embedding : more cli arguments (#7458)

* add parameters for embeddings
--embd-normalize
--embd-output-format
--embd-separator
description in the README.md

* Update README.md

fix tipo

* Trailing whitespace

* fix json generation, use " not '

* fix merge master

* fix code formating
group of parameters // embedding
print usage for embedding parameters

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Co-authored-by: Brian <[email protected]>

Author: YannFollet