Document capabilities in `docs` directory

It would be cool to detail all of the different things we have enabled in https://github.com/containers/ramalama-stack/blob/main/src/ramalama_stack/ramalama-run.yaml in terms of Llama Stack providers and gave some context and examples around these to show what you can do with `ramalama-stack` beyond the basic inference test details in the README

Start with src/ramalama_stack/ramalama-run.yaml to inventory the enabled Llama Stack providers and capabilities, then review the existing inference details in README. Add documentation in the docs directory with context and examples for each capability, showing what ramalama-stack supports beyond the basic inference test.

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