doc: add references to hugging face GGUF-my-repo quantisation web tool. (#7288)

* chore: add references to the quantisation space.

* fix grammer lol.

* Update README.md

Co-authored-by: Julien Chaumond <julien@huggingface.co>

* Update README.md

Co-authored-by: Georgi Gerganov <ggerganov@gmail.com>

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Co-authored-by: Julien Chaumond <julien@huggingface.co>
Co-authored-by: Georgi Gerganov <ggerganov@gmail.com>