Adding a new scanner

LLM Guard can be extended to support new scanners, and to support additional models for the existing. These scanners could be added via code or ad-hoc as part of the request.

Extending the input (prompt) scanners

1. Create a new class in the llm_guard/input_scanners that inherits from base.Scanner and implements the scan method. The scan method should return a tuple str, bool, float.
2. Add test cases for the new scanner in tests/input_scanners.
3. Add the new scanner to the llm_guard/input_scanners/__init__.py __all__ enum.
4. Write documentation in the docs/input_scanners folder and add a link to the mkdocs.yml file.
5. Also, add a link to the documentation in README.md, and update the docs/changelog.md file.

Extending the output scanners

1. Create a new class in the llm_guard/output_scanners that inherits from base.Scanner and implements the scan method. The scan method should return a tuple str, bool, float.
2. Add test cases for the new scanner in tests/output_scanners.
3. Add the new scanner to the llm_guard/output_scanners/__init__.py __all__ enum.
4. Write documentation in the docs/output_scanners folder and add a link to the mkdocs.yml file.
5. Also, add a link to the documentation in README.md, and update the docs/changelog.md file.