add dotpay milestone 1

[fanux]

Milestone Delivery Checklist

• The milestone-delivery-template.md has been copied and updated.
• The invoice form 📝 has been filled out for this milestone.
• This pull request is being made by the same account as the accepted application.
• In case of acceptance, the payment will be transferred to the BTC/ETH payment address provided in the application.
• The delivery is according to the Guidelines for Milestone Deliverables.

Link to the application pull request: w3f/Grants-Program#715