Document RSA absent-parameter algorithms

Author: thieman

src/verify.rs

@@ -35,6 +35,8 @@ pub static SUPPORTED_SIG_ALGS: WebPkiSupportedAlgorithms = WebPkiSupportedAlgori
         RSA_PSS_SHA512,
         RSA_PSS_SHA384,
         RSA_PSS_SHA256,
+        // RFC 4055 requires accepting sha*WithRSAEncryption AlgorithmIdentifiers both with
+        // explicit NULL parameters and with parameters absent in certificate signatures.
         RSA_PKCS1_SHA512,
         RSA_PKCS1_SHA512_ABSENT_PARAMS,
         RSA_PKCS1_SHA384,