Select and document a donation provider and receiving-entity requirements

[mozrin]

Parent

#45

Acceptance criteria

• Compare suitable providers, including GitHub Sponsors where eligible, for fees, geography, payouts, privacy, recurring support, and public donor display.
• Confirm the receiving legal entity, tax language, required disclosures, refunds, and chargeback process before launch.
• Document the decision and provider account ownership; do not publish a payment link until approved.