🚀 Docs: Add Quickstart to README

[jongalloway]

A newcomer-friendly Quickstart to run NLWebNet in <10 minutes.

Scope

• Add a Quickstart section to the root README.md with:
  • Install package via NuGet (library)
  • Run the demo sample (dotnet run) and via Docker
  • Minimal config hints
• Link to doc/demo-setup-guide.md and doc/multi-backend-configuration.md for details

Acceptance Criteria

• A new user can:
  • Install the package
  • Run the demo locally and via Docker
  • Find links to deeper docs

Labels: docs, good first issue