[`docs`] Add starcoder2 docs (#29454)
* add accelerate docs
* Apply suggestions from code review
Co-authored-by: Loubna Ben Allal <44069155+loubnabnl@users.noreply.github.com>
* Update starcoder2.md
* add correct generation
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Co-authored-by: Loubna Ben Allal <44069155+loubnabnl@users.noreply.github.com>