Provided initial draft of contributing guide.

Author: christophenoel

CONTRIBUTING.md

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+# Contributing Guide
+
+> This guide is a draft under construction.
+
+## 1. Read the specification
+
+Consult the latest Editor’s Draft before proposing changes:
+
+* HTML: [https://zarr.dev/geozarr-spec/documents/standard/template/geozarr-spec.html](https://zarr.dev/geozarr-spec/documents/standard/template/geozarr-spec.html)
+* PDF: [https://zarr.dev/geozarr-spec/documents/standard/template/geozarr-spec.pdf](https://zarr.dev/geozarr-spec/documents/standard/template/geozarr-spec.pdf)
+
+## 2. Understand GeoZarr objectives
+
+GeoZarr does not define a new data model. It provides an encoding and mapping to Zarr aligned with CDM-friendly frameworks and formats. Background: [https://medium.com/@christophe.noel/geozarr-1-0-objectives-cf4f9a777a0d](https://medium.com/@christophe.noel/geozarr-1-0-objectives-cf4f9a777a0d)
+
+## 3. Scope and workflow for changes
+
+* Avoid modifying multiple sections at once.
+* Propose initial changes in a focused section.
+* Use GitHub issues for discussion before drafting large updates.
+* Create a branch in the main repository for visible collaborative work.
+
+## 4. Participation
+
+* All community members may comment on issues and pull requests.
+* Monthly OGC GeoZarr SWG meetings provide a forum to review open work.
+* Example datasets can be contributed to [https://github.com/developmentseed/geozarr-examples](https://github.com/developmentseed/geozarr-examples).
+
+## 5. Maintenance structure
+
+### Write access
+
+Granted to a defined maintenance team. This includes SWG chairs and additional contributors approved by them.
+
+### Review and approval
+
+Informal reviews may involve any participant.
+For contested matters, only designated OGC GeoZarr SWG voting members may cast formal votes.
+
+### Pull request process
+
+* PRs are reviewed during regular SWG meetings.
+* Consensus is required for merge.
+* If consensus cannot be reached, an OGC formal vote may be initiated by email.
+* PR authors should ensure that discussion items are placed on the next SWG meeting agenda.
+
+## 6. Versioning and releases
+
+The group follows semantic versioning for official releases. Minor editorial or encoding improvements may occur between major releases when consensus allows.
+
+## 7. Roadmap
+
+Work should follow the priorities defined in the roadmap:
+[https://github.com/zarr-developers/geozarr-spec/wiki/First-Release-RoadMap](https://github.com/zarr-developers/geozarr-spec/wiki/First-Release-RoadMap)