Add contributing guidelines to CONTRIBUTING.md

This document outlines the guidelines for contributing to the project, including ways to contribute, workflow, code standards, commit messages, pull requests, documentation, licensing, and getting help.

Author: WebSupportAtStatsNZ

CONTRIBUTING.md

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+Thank you for your interest in contributing to this project.
+These guidelines explain how to contribute code, documentation, or feedback to repositories under the Statistics NZ GitHub Organization.
+
+# 1. Ways to contribute
+
+You can contribute by:
+
+* Reporting bugs or issues
+* Suggesting enhancements
+* Submitting code (new features/ bug fixes)
+* Improving documentation (README, Wiki, tutorials)
+
+# 2. Workflow
+a. Fork and branch
+* Fork the repository to your own GitHub account
+* Create a new branch for your code development:
+
+```
+git checkout -b feature/<short-description>
+```
+
+* Use clear, descriptive branch names (e.g., ```bugfix/fix-sql-query```)
+
+b. Code Standards
+* Follow the coding standards for the relevant programming language (R, Phyton, SAS, SQL, JavaScript, etc.)
+* Write clean, well-documented code
+* Include comments for complex logic
+* Add or update test where possible
+
+c. Commits
+Use clear, descriptive commit messages:
+```
+[git command]: "Short summary"
+```
+Examples: 
+```
+git commit -m "Fix: corrected null handling in SQL query"
+
+git commit -m "feat: added R function for time series interpolation"
+```
+
+d. Pull Request (PRs)
+* Targer the ```uat``` or ```dev``` branch for testing and integration
+* PRs to ```main/master``` (production) are only made by mainteners/owners after quality assurance testing
+* Each PR should include:
+  - Reference to related issue(s) (e.g., ```Fixes #42```)
+  - Contain a clear description of the change
+  - Pass automated checks (linting, unit tests)
+
+# 3. Documentation
+* Update the ```README.md``` if your change affects usage
+* Add Roxygen2 style comments to explain new functions, workflows, or data transformations
+* Follow the repository structure for documentation
+
+# 4. Licensing and Data Protection
+* All contributors must comply with the **Crown Copyright** license unless otherwisew specified.
+* Do not commit sensitive data, credentials, or unpublished statistics
+* Ensure that any third-party libraries or code comply with the approved licenses listed in the repository
+
+# 5. Getting help
+If you are unsure about how to contribute, please:
+
+* Open a discussion in the respository's **Issues** section
+* Contact the repository maintainers
+* If repository maintainers not available, contact the admninistrator: githubadmin@stats.govt.nz