arx-ecosystem: Repository, Process & Internal Maps

8 imported docs from arx-ecosystem.

Document	Repository	Source path
ARX App Catalog Model	arx-ecosystem	`docs/app-catalog-model.md`
ARX Ecosystem	arx-ecosystem	`README.md`
Changelog	arx-ecosystem	`CHANGELOG.md`
Completeness Model	arx-ecosystem	`docs/COMPLETENESS_MODEL.md`
Contributing	arx-ecosystem	`CONTRIBUTING.md`
Implementation Inventory	arx-ecosystem	`docs/IMPLEMENTATION_INVENTORY.md`
Publication Workflow	arx-ecosystem	`docs/publication-workflow.md`
Repository Boundaries	arx-ecosystem	`docs/REPO_BOUNDARIES.md`