Restore CLI entrypoint and add CI workflow

[devblac]

Summary

• add a cmd/docker-lint entrypoint that wires parser, analyzer, and formatters to match documented flags
• introduce a GitHub Actions workflow running tests with coverage and uploading results to Codecov, updating badges accordingly
• align documentation and ignore rules with the Go 1.22 requirement and new CLI path
• update the module path and import references to github.com/devblac/docker-lint so badges, go install, and imports match the repository owner

Testing

• go test ./...

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Codex Task