Support HashAlgorithm class

[ghost]

Sha3Digest class (namespace Org.BouncyCastle.Crypto.Digests) can provide the Hash function, but it is not the C# programing style.

Most C# Hash classes inherit from class HashAlgorithm (namespace System.Security.Cryptography). By inheriting from HashAlgorithm, a large number of C# codes can be seamlessly switched.

https://docs.microsoft.com/en-us/dotnet/api/system.security.cryptography.hashalgorithm

This github class library has realized this function, through the simple conversion, bouncycastle can be integrated into all applications more easily.

https://github.com/dariogriffo/sha3.net/blob/master/src/SHA3.Net/Sha3.cs

[peterdettman]

Our API makes little to no attempt to integrate into System.Security.Cryptography API, and it wouldn't make much sense to do so on a case-by-case basis. I'm not saying it would be a terrible idea, but it's a much larger question than SHA3.

If you want to PR a HashAlgorithm adapter class that adapts any IDigest into a HashAlgorithm, that might be easy to include.