Why I am facing error in verifying a JWT token using `jsonwebtoken` module?

Question

I am working on a Next.js app using Firebase authentication. I have managed to implement an authentication system that also generates a session-cookie (in simple words a token we get after successful authentication using getIdToken()). I need to verify it in my app for some reasons. As per the official documentation of Firebase:

Finally, ensure that the ID token was signed by the private key corresponding to the token's kid claim. Grab the public key from https://www.googleapis.com/robot/v1/metadata/x509/[email protected] and use a JWT library to verify the signature. Use the value of max-age in the Cache-Control header of the response from that endpoint to know when to refresh the public keys.

I don't understand how can I verify the token using the same. I have simply copy-pasted key from the URL provided above and replaced all \n with new line. Here is what I have tried:

const publicKey = `-----BEGIN CERTIFICATE-----
  MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCsz8sS5pS6KBoX1ph7IXEdfUhv
  PA7S5Eg5B9sPSLrEVtowMGXxpVSJXoJdN8aPP8NrZq0MhW1dHL//Uqg0TTtBv+8F
  IV9SgXrrbHv7jFtwWWqSALwy6XFs+hPi2ES7OOIPxKtkm1n8tMF0dTjrxPR56xCz
  qwuewD5JGJhPWdgJbQIDAQAB
  -----END CERTIFICATE-----`

  jwt.verify(
    cookieValue,
    publicKey,
    { algorithms: ["RS256"] },
    (err, decoded) => {
      if (err) {
        console.error("Token verification failed:", err.message);
      } else {
        console.log("Token verified successfully:", decoded);
      }
    }
  );

But I am getting error: Token verification failed: secretOrPublicKey must be an asymmetric key when using RS256 each time. I have tried to put the key in different string formats but still.