Operation request: RSA Key Modulus

## Summary
Would love to have the ability to calculate an RSA key's modulus. Very helpful in [verifying the private key matches the public (x509) cert](https://knowledge.digicert.com/solution/SO29559.html). Example `openssl` invocation:

```bash
openssl rsa -noout -modulus -in rsa.key
```

The `Parse X.509 certificate` already provides the public cert modulus, and in theory a well-crafted recipe would be able to compare both?

### Example Input
```
-----BEGIN PRIVATE KEY-----
someRAndoMkeyMATerial
-----END PRIVATE KEY-----
```
### Example Output
```
ABCDEF0123456789......
```