chore: prepare comparator as a stdlib-only open-source Go library

[christiangda]

Summary

Prepares comparator to be published as a proper open-source Go library, modeled on the structure of slashdevops/e5t. The library targets Go 1.26 and now depends on the Go standard library only — no third-party modules.

Changes

🧹 Stdlib-only + best practices

• Removed the external github.com/aizon-shared/ds-utils/pkg/testutils dependency (its single use is replaced with clearly-marked inline test values). Verified with go list -deps — zero external dependencies.
• Modernized benchmarks to the Go 1.24+ for b.Loop() form, dropping redundant b.ResetTimer() calls.
• Follows the Google Go Style Guide (uses any, small focused funcs, documented API).

📖 Documentation

• Renamed docs.go → doc.go (conventional package-doc filename).
• Rewrote the README.md: CI / Go Reference / Go Report Card / license / release badges, emoji section headers, go get install & update instructions, correct github.com/slashdevops/comparator module path, and links into the docs.
• Added an extensive docs/ folder: getting-started, configuration, diffing, output-formats, json-patch, custom-comparators, performance, and FAQ.
• Added runnable Example functions for the options and package-level API (comparator_options_examples_test.go), all verified by go test.

⚙️ Open-source scaffolding & CI/CD

• Apache-2.0 LICENSE, SECURITY.md, .gitignore, .golangci.yaml, .vscode/settings.json.
• .github/ metadata: Dependabot, release-notes config, Copilot instructions, CodeQL config.
• GitHub Actions: main.yml, pr.yml, release.yml, and codeql.yml.

Verification

gofmt -l .        # clean
go vet ./...      # clean
go build ./...    # ok
go test -race ./... -covermode=atomic   # PASS, 87.9% coverage
go list -deps ... # no external deps

🤖 Generated with Claude Code

[github-advanced-security]

You are seeing this message because GitHub Code Scanning has recently been set up for this repository, or this pull request contains the workflow file for the Code Scanning tool.

What Enabling Code Scanning Means:

• The 'Security' tab will display more code scanning analysis results (e.g., for the default branch).
• Depending on your configuration and choice of analysis tool, future pull requests will be annotated with code scanning analysis results.
• You will be able to see the analysis results for the pull request's branch on this overview once the scans have completed and the checks have passed.

For more information about GitHub Code Scanning, check out the documentation.