add digest, http_test

digest/digest.dart

@@ -0,0 +1,12 @@
+import 'dart:convert';
+import 'package:crypto/crypto.dart';
+
+// https://pub.dev/packages/crypto
+main() async {
+  var bytes = utf8.encode("Hello World!");
+
+  var digest = sha256.convert(bytes);
+
+  // print("Digest as bytes: ${digest.bytes}");
+  print("Digest as hex string: $digest");
+}