[governance] Create OKDP/.github org-level community health files

[jpmewenemesse]

Description

Create the OKDP/.github repository with default community health files that GitHub
automatically applies to all OKDP repos.

See: https://docs.github.com/en/communities/setting-up-your-project-for-healthy-contributions/creating-a-default-community-health-file

Deliverables

• Create OKDP/.github repository
• CODE_OF_CONDUCT.md (Contributor Covenant v2.1)
• CONTRIBUTING.md (contribution guide, repo map, PR process)
• SECURITY.md (vulnerability reporting)
• PULL_REQUEST_TEMPLATE.md (generic PR checklist)
• ISSUE_TEMPLATE/bug_report.md
• ISSUE_TEMPLATE/feature_request.md
• SUPPORT.md (how to get help)
• GOVERNANCE.md (org-wide decision-making, repo structure, roles...)
• profile/README.md (org landing page at github.com/OKDP)

Acceptance Criteria

• All OKDP repos show community health files in GitHub UI
• New issues on any OKDP repo show the bug report / feature request templates
• New PRs on any OKDP repo show the PR template
• github.com/OKDP shows the org profile README