Streamline README quick start with bundled context sample

[rekby]

Summary

• highlight the bundled sf.Context fixture in the README quick start so newcomers can get running without writing custom helpers
• keep the custom counter example concise and point readers to the getting-started guide to reduce duplication

Testing

• go test ./...

[github-actions]

API Changes

summary

Base version: v0.7.1 (latest)
Suggested version: v0.7.2

[Copilot]

Pull Request Overview

This PR enhances the README quick start section by highlighting the bundled sf.Context fixture, making it easier for newcomers to start using Fixenv without writing custom helpers. The PR also adds comprehensive documentation pages and example tests demonstrating the prebuilt fixtures.

Key changes include:

• Streamlined README with better structure and clearer quick start examples featuring bundled fixtures
• New documentation structure with guides on getting started, scopes, cleanup, and advanced patterns
• Example tests demonstrating the sf helper fixtures (Context, TempDir, LocalTCPListener)

Reviewed Changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
README.md	Complete restructure with improved quick start, feature highlights, documentation links, and comparison table
docs/getting-started.md	New guide covering installation, first fixtures with both bundled and custom examples
docs/scopes-and-lifetimes.md	New guide explaining scope options and parameterised fixtures
docs/cleanup-and-ordering.md	New guide on cleanup callbacks and execution order
docs/advanced-fixtures.md	New guide covering fixture composition, custom environments, and observability
docs/examples/README.md	New walkthrough documentation for all example projects
docs/README.md	New documentation index linking to all guides
examples/sf_helpers/context_fixture_test.go	New test demonstrating sf.Context lifecycle
examples/sf_helpers/tempdir_fixture_test.go	New test demonstrating sf.TempDir cleanup
examples/sf_helpers/tcp_listener_fixture_test.go	New test demonstrating sf.LocalTCPListener scoping
examples/custom_env_with_shared_content/custom_env_with_shared_content_test.go	Removed file (appears to be consolidating examples)

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.