Examples using powershell use [Security.Cryptography.X509Certificates.X509Certificate2] to sign data. The data present here is in the form of what I believe is a Json Web Key (JWK).
How do you convert a JWK to a compliant cert that can be used by X509Certifate2?
https://www.googleapis.com/oauth2/v1/certs gives you the X509 certificates in PEM format, but I believe this endpoint is deprecated.