Shieldgemma2 (#36678)
* single commit
* correct config
* fixup
* dummy pt
* Use ShieldGemma2Config in conversion script
* Update src/transformers/models/shieldgemma2/configuration_shieldgemma2.py
* Adding shieldgemma2 to models.__init__.py
* Adding ShieldGemma2 to main __init__.py
* Update shieldgemma2.md
* Update shieldgemma2.md
* Adding tests. Addressing review feedback.
* Minor docs update
* Fixing code quality feedback from CI
* Fixing empty messages bug reported by ghunkins
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Co-authored-by: Arthur Zucker <arthur.zucker@gmail.com>
Co-authored-by: Ren Pang <ain-soph@live.com>
