message: flexbuffers blob to string implementation
diff: @@ -547,6 +547,9 @@ class Reference {
  AppendToString<TypedVector>(s, AsTypedVector(), keys_quoted);
  } else if (IsFixedTypedVector()) {
  AppendToString<FixedTypedVector>(s, AsFixedTypedVector(), keys_quoted);
  + } else if (IsBlob()) {
  + auto blob = AsBlob();
  + flatbuffers::EscapeString(reinterpret_cast<const char*>(blob.data()), blob.size(), &s, true, false);
  } else {
  s += "(?)";
  }
  