docs : how to add a model (#6565)
* docs: how to add a model
* docs: model: typo and docs
* docs: model: add prevision on RoPE
* docs: model: rephrasing README.md
* docs: model: rephrasing README.md
* docs: model: README.md fix trailing spaces
* docs : some fixes
* Update README.md
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Co-authored-by: Georgi Gerganov <ggerganov@gmail.com>
