Release 0.2.4 with CONTRIBUTING and Ruby bump

* Add CONTRIBUTING.md with a comprehensive contributor guide covering Code of Conduct, prerequisites, fork/clone and setup instructions, development workflow, testing and coverage requirements, RuboCop/style rules, performance guidance and benchmarks, making changes, PR submission checklist, automated release process, project structure, resources, and contact information
* Require Ruby 3.2.0 or higher in README
* Bump VERSION to '0.2.4' in lib/domain_extractor/version.rb

Author: jordanhudgens