docs: use the API table format in README

[lesnik512]

Summary

The API section used dash bullets while the other integration READMEs use a Symbol/Description table (e.g. modern-di-aiohttp). The context-provider entry lacked its scope.

Evidence:

• modern_di_faststream/main.py:14: faststream_message_provider is Scope.REQUEST.
• modern_di_faststream/main.py:108-110: FromDI(dependency, *, use_cache=True, cast=False) (already correct, kept).
• install_middleware raises RuntimeError when the app has no broker.

Changes

• Convert the API bullets to the table format.
• Add (REQUEST scope) to the context provider row; name the RuntimeError and the return value of setup_di.
• Footer: "with IoC container" -> "with an IoC container", and the org-profile line no longer uses a dash.

Checklist

• Lint and format pass (ruff)
• Type check passes (ty)
• Tests pass and new behavior is covered
• Build succeeds (uv build) if packaging or build config changed
• Repo metadata stays consistent across the three surfaces (GitHub description, pyproject description, profile blurb) if this touches packaging

Docs-only change. just lint-ci and just test pass; no mkdocs.yml in this repo.