Automate the lists of the MAINTAINERS on the ci.yaml

[hideokamoto-stripe]

Ref: #1612

We need to automate to update the MAINTAINERS value on the .github/workflows/ci.yaml.
https://github.com/stripe-samples/accept-a-payment/blob/main/.github/workflows/ci.yml#L12-L19

Possibly using GitHub API to list the maintainers and update it.