Append an Iterable list of objects to the description, using the
specified separator and framing the list with start
and end.
Source
Description addAll(
String start, String separator, String end, Iterable list) {
var separate = false;
add(start);
for (var item in list) {
if (separate) {
add(separator);
}
addDescriptionOf(item);
separate = true;
}
add(end);
return this;
}