Add LinkedList

[sethladd]

Found this: https://github.com/dart-lang/web-ui/blob/master/lib/src/linked_list.dart

The linkedlist in dart:collection is hard to use, as it forces all entries to extend from LinkedListEntry.

Quiver should have an easy to use linked list.

Thanks!

[lrhn]

Is this a case of the Dart Queue classes not being very discoverable?
The DoubleLinkedQueue implements all the operations of this LinkedList class (but the author knows that because he used the queue code as base for this "list" code, so it seems he just wanted another name for it).

[sethladd]

This might be a case of the API docs for Queue not pointing to Queue's default implementation, and the API docs of Dart's LinkedList not pointing back to Queue as an out-of-the-box option.

I will close this, as it looks like Dart has an answer. It's just not obvious.