Add tests for SHAx.calculate() public access. Update MD5 public access.

Sources/CryptoSwift/MD5.swift

@@ -43,7 +43,7 @@ public final class MD5: DigestType  {
         
     }
 
-    func calculate(for bytes: Array<UInt8>) -> Array<UInt8> {
+    public func calculate(for bytes: Array<UInt8>) -> Array<UInt8> {
         do {
             return try self.update(withBytes: bytes, isLast: true)
         } catch {

Tests/CryptoSwiftTests/Access.swift

@@ -34,7 +34,11 @@ class Access: XCTestCase {
         let _ = Digest.sha512([1,2,3])
         let _ = Digest.sha3([1,2,3], variant: .sha224)
 
-        let _ = MD5()
+        let _ = SHA1().calculate(for: [0])
+        let _ = SHA2(variant: .sha224).calculate(for: [0])
+        let _ = SHA3(variant: .sha256).calculate(for: [0])
+
+        let _ = MD5().calculate(for: [0])
     }
 
     func testArrayExtension() {