docs(governance): add first-time contributor policy

[babatundealao407-alt]

Summary

• add the versioned first-time contributor policy under Governance/policies/
• define the reserved good-first-issue pool, maintainer support, mentorship expectations, and review path
• keep the change limited to the Governance folder as required by the issue

Validation

• git diff --check

Closes #1608

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[babatundealao407-alt]

@RUKAYAT-CODER @babatundealao407-alt Implemented and pushed the first-time contributor policy in 1b9795ab. It defines the reserved good-first-issue pool, maintainer support, mentorship expectations, and review path, limited to Governance/. Closes #1608 is included in the PR body.

[RUKAYAT-CODER]

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