Add Digest.hashCode.

lib/src/digest.dart

Index: lib/src/digest.dart
diff --git a/lib/src/digest.dart b/lib/src/digest.dart
index 2e92fe21c48485844a2ad9f54d3ff4b361c9d807..f33752afaee67939902e22217d06a582ba4f7767 100644
--- a/lib/src/digest.dart
+++ b/lib/src/digest.dart
@@ -2,6 +2,7 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+import 'package:collection/collection.dart';
 import 'package:convert/convert.dart';
 
 /// A message digest as computed by a [Hash] or [HMAC] function.
@@ -28,6 +29,8 @@ class Digest {
     return result == 0;
   }
 
+  int get hashCode => const ListEquality().hash(bytes);
+
   /// The message digest as a string of hexadecimal digits.
   String toString() => hex.encode(bytes);
 }