feat: add openpayment

[vittominacori]

Description

Add OpenPayment to Ecosystem as Client-Side Integrations.

Documentation is available here: https://openpayment.link/docs/

Here a working Payment Link using x402: https://openpayment.link/pay/?paymentId=ed5b8e83-607b-4853-90c6-f4f3ba821424

Checklist

• I have formatted and linted my code
• All new and existing tests pass
• My commits are signed (required for merge) -- you may need to rebase if you initially pushed unsigned commits
• I added a changelog fragment for user-facing changes (docs-only changes can skip)

[cb-heimdall]

🟡 Heimdall Review Status

Requirement	Status	More Info
Reviews	🟡 0/1	Denominator calculation Show calculation 1 if user is bot 0 1 if user is external 0 2 if repo is sensitive 0 From .codeflow.yml 1 Additional review requirements Show calculation Max 0 0 From CODEOWNERS 0 Global minimum 0 Max 1 1 1 if commit is unverified 0 Sum 1

[vercel]

@vittominacori is attempting to deploy a commit to the Coinbase Team on Vercel.

A member of the Team first needs to authorize it.

[vittominacori]

Hi @Must-be-Ash
Any chance to check this PR?